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The distribution of species and the way that lineages are structured are the result of intrinsic historical processes of the species and their relationships with landscape features. Paleosuchus palpebrosus is one of the smallest crocodilians in the world and has a wide geographic distribution in South America, occurring in different habitats. Here, we analyzed mitochondrial cytochrome b sequences of 227 individuals, investigated how elements of landscape heterogeneity impact genetic differentiation, and evaluated the evolutionary and phylogeographic history of the species. Thus, we hypothesized that landscape structures, such as aridity and slope, should act as resistance surfaces to population connectivity, while rivers could mediate the dispersion of the species as a conductor of the gene flow. The analyses recovered three main lineages of P. palpebrosus. While most of the observed genetic variation was explained by geographic resistance distance, river connectivity had a smaller contribution for the observed variation. We also found a recent history with limited genetic divergence throughout the wide distribution of the species. Our findings highlight the main drivers for the evolutionary history of the species and how landscape features can shape the diversification, especially if we consider rivers as a facilitator of gene flow. [ABSTRACT FROM AUTHOR]

Simple Summary: Crocodiles are one of nature's most successful predators. Their prey varies according to their size. Adults are known to consume different types of vertebrates; juveniles have a similar diet, although their prey is smaller. However, hatchlings have a diet based mainly on insects. This study aimed to know the diet of hatchling Morelet's crocodiles (Crocodylus moreletii) at a growth stage corresponding to their transition to the juvenile stage. Therefore, it is important to know which vertebrate prey are beginning to appear during this developmental change in crocodiles. To find out, we captured and washed the stomachs of 31 hatchling crocodiles in the Laguna de las Ilusiones in Tabasco, Mexico. Our results showed that crocodiles have a generalist diet, with prey ranging from invertebrates (mainly coleoptera and hemipterans) to some vertebrates (mostly fish and birds). It is important to know these changes in the diet of crocodilians as they develop to help us better interpret their natural history and propose better strategies for their study. The relationship between diet and behavior is essential to understanding an animal's strategies to obtain food, considering ontogenical changes. In reptiles, there is a relationship between the length of the individual and the size of the prey it consumes. Studies have focused on the ontogenetic changes in reptile diets from hatchling to adult, but only a few studies have focused on the transition from hatchling to juvenile. We aimed to describe and analyze the composition, variation, diversity, and overlap in the diet of hatchling Morelet's crocodiles (Crocodylus moreletii) for three size intervals during the hatchling–juvenile transition. We captured 31 hatchling Morelet's crocodiles in an urbanized lagoon in Tabasco. We performed stomach-flushing to determine the diet. Additionally, we estimated the volume, frequency of occurrence, and relative importance of diet items and analyzed the relationship between prey type and the total length of the individuals. The diversity of the hatchling prey suggests a generalist diet. We observed two items not previously described in the diet of hatchling crocodiles. In addition, we found differences in diet between the initial and final size intervals, as increases in the length of prey appeared that they did not consume when they were hatchlings. Our results contribute new information to the dietary changes that occur during the hatchling–juvenile transition. [ABSTRACT FROM AUTHOR]

In an age of emerging zoonoses, it is important to understand the intricate system of vectors and reservoirs, or hosts, and their relation to humans. West Nile Virus (WNV) has been detected in a myriad of nonhuman hosts. Transmission of the virus to humans is reliant on amplified seroprevalence within the host, which occurs primarily in birds. However, recent studies have found that other animal groups, including crocodilians, can obtain seroprevalence amplification to levels that make them competent hosts able to transmit WNV to mosquitoes, which can then transmit to humans. Climate change could exacerbate this transmission risk by shifting the distributions of mosquito vectors towards novel geographic ranges. Here, we use maximum entropy models to map the current and future distributions of three mosquito vector species and four crocodilian species in North America to determine the emerging risk of WNV outbreaks associated with changing climates and WNV associated with crocodilians in North America. From our models, we determined that one mosquito species in particular, Culex quinquefasciatus, will increase its distribution across the ranges of all crocodilian species in all tested climate change scenarios. This poses a potential risk to public health for people visiting and living near crocodilian farms and high-density natural crocodilian populations. [ABSTRACT FROM AUTHOR]

Extant crocodilian jaws are subject to functional demands induced by feeding and hydrodynamics. However, the morphological and ecological diversity of extinct crocodile-line archosaurs is far greater than that of living crocodilians, featuring repeated convergence towards disparate ecologies including armoured herbivores, terrestrial macropredators and fully marine forms. Crocodile-line archosaurs, therefore, present a fascinating case study for morphological and functional divergence and convergence within a clade across a wide range of ecological scenarios. Here, we build performance landscapes of two-dimensional theoretical jaw shapes to investigate the influence of strength, speed and hydrodynamics in the morphological evolution of crocodile-line archosaur jaws, and test whether ecologically convergent lineages evolved similarly optimal jaw function. Most of the 243 sampled jaw morphologies occupy optimized regions of theoretical morphospace for either rotational efficiency, resistance to Von Mises stress, hydrodynamic efficiency or a trade-off between multiple functions, though some seemingly viable shapes remain unrealized. Jaw speed is optimized only in a narrow region of morphospace whereas many shapes possess optimal jaw strength, which may act as a minimum boundary rather than a strong driver for most taxa. This study highlights the usefulness of theoretical morphology in assessing functional optimality, and for investigating form–function relationships in diverse clades. [ABSTRACT FROM AUTHOR]

The principal effect controlling the oxygen affinity of vertebrate haemoglobins (Hbs) is the allosteric switch between R and T forms with relatively high and low oxygen affinity respectively. Uniquely among jawed vertebrates, crocodilians possess Hb that shows a profound drop in oxygen affinity in the presence of bicarbonate ions. This allows them to stay underwater for extended periods by consuming almost all the oxygen present in the blood-stream, as metabolism releases carbon dioxide, whose conversion to bicarbonate and hydrogen ions is catalysed by carbonic anhydrase. Despite the apparent universal utility of bicarbonate as an allosteric regulator of Hb, this property evolved only in crocodilians. We report here the molecular structures of both human and a crocodilian Hb in the deoxy and liganded states, solved by cryo-electron microscopy. We reveal the precise interactions between two bicarbonate ions and the crocodilian protein at symmetry-related sites found only in the T state. No other known effector of vertebrate Hbs binds anywhere near these sites. Crocodilians are ambush predators that possess haemoglobin with an allosteric switch between R (high oxygen affinity) and T (low oxygen affinity) forms strongly controlled by bicarbonate ions, a unique evolutionary feature that helps the animal to stay underwater for extended periods of time. [ABSTRACT FROM AUTHOR]

The Late Miocene vertebrate fauna from the Entre Ríos Province, Argentina, comes from two units: the marine Paraná Formation and the Lower Member of Ituzaingó Formation (LMIF). This latter includes a lower conglomerate set, with fine quartz gravel, and clay and chalcedony clasts, and fossil remains, traditionally known as ‘Mesopotamiense’ or ‘Conglomerado osífero’. We present new fossil vertebrate remains from the LMIF at the Puerto Víboras locality (Hernandarias, Entre Ríos Province) including Leptodactylus sp. (Amphibia, Anura), Crocodylia indet. Caimaninae indet. and Paranasuchus gasparinae (Alligatoridae), Chelidae indet. (Testudines, Pleurodira), Chelonoidis sp. (Testudines, Cryptodira), Plohophorus paranensis (Cingulata, Glyptodontidae), and Macraucheniinae indet. (Macraucheniidae, Litopterna). The record of Leptodactylus sp. represents the oldest record of the genus and the first amphibian record for the Neogene of the Entre Ríos Province. The material described herein and assigned to Chelonoidis sp. allows to confirm for the first time the presence of a testudinid in the Late Miocene of the Entre Ríos Province. [ABSTRACT FROM AUTHOR]

Reptiles and amphibians are largely present in many environments, including domestic areas when they are kept as pet animals. They often harbor zoonotic pathogens, which can pose a serious risk of infection for humans, mainly immunocompromised individuals, the elderly, children, and pregnant women. Several studies have been carried out to verify the role of cold-blooded animals in the epidemiology of some bacteria, mainly Salmonella, whereas scarce attention has been focused on these animals as a source of staphylococci. These bacteria are often antimicrobial-resistant and they act as opportunistic pathogens, which can cause relevant infections in humans and animals, both domestic and wild. Asymptomatic reptiles and amphibians often harbor staphylococcal strains, such as Staphylococcus aureus and coagulase-negative Staphylococcus spp.; however, these bacteria have been associated with clinical conditions that usually appear in animals under stress conditions. In all cases, greater attention should also be focused on staphylococci in cold-blooded animals due to their implications in human and veterinary medicine. [ABSTRACT FROM AUTHOR]

Fossil feathers have transformed our understanding of integumentary evolution in vertebrates. The evolution of feathers is associated with novel skin ultrastructures, but the fossil record of these changes is poor and thus the critical transition from scaled to feathered skin is poorly understood. Here we shed light on this issue using preserved skin in the non-avian feathered dinosaur Psittacosaurus. Skin in the non-feathered, scaled torso is three-dimensionally replicated in silica and preserves epidermal layers, corneocytes and melanosomes. The morphology of the preserved stratum corneum is consistent with an original composition rich in corneous beta proteins, rather than (alpha-) keratins as in the feathered skin of birds. The stratum corneum is relatively thin in the ventral torso compared to extant quadrupedal reptiles, reflecting a reduced demand for mechanical protection in an elevated bipedal stance. The distribution of the melanosomes in the fossil skin is consistent with melanin-based colouration in extant crocodilians. Collectively, the fossil evidence supports partitioning of skin development in Psittacosaurus: a reptile-type condition in non-feathered regions and an avian-like condition in feathered regions. Retention of reptile-type skin in non-feathered regions would have ensured essential skin functions during the early, experimental stages of feather evolution. The evolution of feathers is associated with the evolution of related skin microstructures. Here, the authors demonstrate that Psittacosaurus, a non-avian feathered dinosaur, retained scaled skin like its ancestors in body regions lacking feathers. [ABSTRACT FROM AUTHOR]

Dwarf caiman species of the genus Paleosuchus (Paleosuchus palpebrosus and Paleosuchus trigonatus) are old, widespread crocodilian lineages with populations affected by habitat modification. For both species, phylogeographical studies revealing crucial information have already been performed, but for important ecoregions, such as the Orinoco, knowledge is lacking. In this study, the phylogenetic identity of individuals of Paleosuchus spp. from the Orinoco basin of Colombia and Venezuela was evaluated. The genetic structure of the two species of Paleosuchus was also determined and their genetic diversity quantified. The results show a marked genetic structuring in both species, also indicating that the populations of P. trigonatus and P. palpebrosus of the Orinoco basin are well differentiated from those of other hydrographic basins. For Colombia, it was possible to infer that there are two independent management units for both species (Orinoco and Amazonas) and that the populations of the Orinoco basin present high genetic and haplotypic diversity. In Venezuela, only one management unit was identified for each species. This finding, together with the results of previous studies, show that, in total, there are at least five management units for P. palpebrosus and six for P. trigonatus , throughout their distribution areas. It is necessary to take this information into account when establishing conservation strategies for these species, although it is stressed that the geographical sampling must be improved in future phylogeographical studies, because information gaps persist at the geographical level. [ABSTRACT FROM AUTHOR]

The gharial Gavialis gangeticus is a Critically Endangered crocodilian currently known from only 14 disjunct locations in Nepal and India. The protected stretch of the Babai River in Bardia National Park, Nepal, is home to one of the six subpopulations of gharials that have exhibited recent evidence of reproduction. However, there is limited information available on the gharial population in this region. We conducted surveys during the breeding, nesting and hatching seasons of gharials during 2020–2022 to study the gharial population in the Babai River in Bardia National Park. We located one breeding group of gharials in Soth Khola (2–3 individuals) and one in Dhanuse (5–6 individuals), and we observed pre-mating or mating behaviours in all 3 years. We identified potential nesting areas on sand banks of 19–175 m in length. During nesting seasons we found abundant signs of nesting only in Dhanuse, including entry and exit trails of female gharials to and from the water and trial nests. In 2020 and 2021 we did not find any signs of hatching, probably because of flooding. In 2022 we recorded two gharial nests, producing c. 60 hatchlings, in Dhanuse. Our findings indicate that the gharial population in the Babai River is probably nesting annually. We recommend various conservation actions for this gharial population. [ABSTRACT FROM AUTHOR]

Location of sound sources is a fundamental task of the auditory system. Recent studies have shown that land vertebrates employ an array of sound localization strategies. We have therefore compared auditory brainstem circuits by measuring cell numbers in the cochlear nuclei in relation to brain weight among different groups of reptiles to determine if these behavioral differences are reflected in the organization of the brainstem. In extant archosaurs, the birds and crocodilians, the two ears are weakly connected pressure receivers, and sound direction is computed by binaural interactions in brain involving parallel processing of interaural time and level differences. The first-order cochlear nuclei are nucleus magnocellularis (NM) and nucleus angularis (NA). NM projects bilaterally to the nucleus laminaris (NL), where interaural time differences are computed in archosaurs. Relative to brain size, NA, NM and NL cell counts of the American alligator (Alligator mississippiensis) are similar to those of birds. Testudines (turtles and tortoises), sister group to archosaurs, are also assumed to compute sound location from binaural interactions in the brain due to weakly connected middle ears. Compared to archosaurs, NA, NM and NL of the red-eared slider (Trachemys scripta), common snapping turtle (Chelydra serpentina) and Hermann’s tortoise (Testudo hermanni) are all proportionally small. In lizards, due to the strong internal coupling of the middle ears, the cochlear nerve responses are directional, and interaural time and level differences are co-dependent and frequency dependent, suggesting that the neural processing of sound direction may be different from archosaurs. Compared to archosaurs, NM and NL of the tokay gecko (Gekko gecko) and green iguana (Iguana iguana) are proportionally small, but NA is well-developed, suggesting a greater importance of the NA pathway for the processing of the high-frequency directional information generated by the coupled ears. Snakes originated from lizard ancestors, but have secondarily lost their eardrums, and their sound localization strategies are unknown. NA and NM of the western ratsnake (Pantherophis obsoletus) are proportionally smaller than those of the lizards.

Pharmacokinetics studies of anesthetic agents are important for understanding of the pharmacology and metabolism of anesthetic agents in reptilians. This study was designed to examine the pharmacokinetic and pharmacodynamic properties of intravenous dextroketamine alone or combined with midazolam in Caiman crocodilus. Eight caimans were anesthetized with dextroketamine (10 mg/kg; group D) or dextroketamine and midazolam (10 and 0.5 mg/kg respectively; group DM) into the occipital venous sinus. The pharmacokinetic parameters were calculated by HPLC using a non‐compartmental modeling. Serial blood samples were collected at baseline and within 15 and 30 min, and 11.5, 2, 4, 8, 12, 24 and 48 h of drug administration. Sedation status over time differed between groups. All animals in group D (8/8; 100%) showed signs of light sedation at t10. Half (4/8; 50%) of these caimans did not progress to deeper levels of sedation. In spite of light sedation at t10, animals in group DM were deeply sedated within 13.13 ± 7.04 min of anesthetic agent injection. The area under the plasma concentration–time curve (AUC0–48) and half‐life of dextroketamine changed significantly after combination with midazolam. Even without significant changes in clearance, the almost two‐fold increase in the half‐life of dextroketamine suggests a slower rate of elimination. [ABSTRACT FROM AUTHOR]

Historical and recent arrivals of crocodilians to the Gulf of Guinean Oceanic Island of São Tomé have intrigued naturalists for several centuries. Here we present the revision of the historical records, and present data regarding the recent arrival of a single specimen in 2021. After being killed by the local authorities, the specimen was preserved and studied both through morphological and molecular methods. Our findings suggest that the specimen was a sub-adult Nile crocodile, Crocodylus niloticus Laurenti, 1768, which most likely drifted from the Congo or Ogooué river mouths in West Africa by the oceanic current acting on the Gulf of Guinea. The story of this individual highlights the dispersion paths that have contributed by the past biological colonization of São Tomé Island. [ABSTRACT FROM AUTHOR]

A case of a non-fatal crocodile attack on a human was reported on the banks of the Segovia River on the Honduras and Nicaragua border. The 12-year-old girl survived the attack, only with damage to the tibia of her right leg, where she lost part of the muscle tissue due to the bite. It was after the attack that the American crocodile was shot and killed by local people. In this paper, we discuss the possible causes of crocodile attacks. [ABSTRACT FROM AUTHOR]

Purpose: Little is known about the coccidian parasites of the American alligator, Alligator mississippiensis (Daudin). To date, only two species of Eimeria Schneider, 1875 have been previously reported from A. mississippiensis. Here, we report from mensural and morphometric data on two new species of Eimeria from A. mississippiensis from Georgia, USA. Methods: Fresh feces were collected in June 2023 from a single captive juvenile male A. mississippiensis. Multiple samples were placed in individual zip-lock bags and aqueous potassium dichromate was added. They were examined for sporulated oocysts after flotation in Sheather's sugar solution, measured, and photographed. Results: Samples contained oocysts representing two new species of Eimeria. Oocysts of Eimeria tellezae n. sp. are subspheroidal to ellipsoidal with a pitted bi-layered wall, measure (L × W) 34.5 × 31.5 µm, and have a length/width (L/W) ratio of 1.1; a micropyle and polar granule were absent but an oöcyst residuum was present. Sporocysts are ellipsoidal and measure 17.2 × 7.7 µm, L/W 2.2; a nipple-like Stieda body bearing one to several filaments was present but sub-Stieda and para-Stieda bodies were absent. The sporocyst residuum is composed of various-sized granules in a compact rounded or irregular mass, sometimes dispersed between the sporozoites. Oocysts of Eimeria daudini n. sp. are ellipsoidal with a pitted bi-layered wall, measure (L × W) 32.5 × 20.2 µm, and have a length/width (L/W) ratio of 1.6; a micropyle and polar granule were absent but an oöcyst residuum was present. Sporocysts are ellipsoidal and measure 15.4 × 7.4 µm, L/W 2.1; a nipple-like Stieda body bearing one to several filaments was present but sub-Stieda and para-Stieda bodies were absent. The sporocyst residuum is composed of various-sized granules in a compact rounded or irregular mass, sometimes dispersed between the sporozoites. Both new species can readily be distinguished from previously described eimerians from crocodilians, including those from A. mississippiensis. Conclusion: We document two new species of Eimeria from the American alligator. Currently, four species of Eimeria are known from A. mississippiensis examined from both east and west of the Mississippi River, USA. [ABSTRACT FROM AUTHOR]

Trait datasets are increasingly being used in studies investigating eco-evolutionary theory and global conservation initiatives. Reptiles are emerging as a key group for studying these questions because their traits are crucial for understanding the ability of animals to cope with environmental changes and their contributions to ecosystem processes. We collected data from earlier databases, and the primary literature to create an up-to-date dataset of reptilian traits, encompassing 40 traits from 12060 species of reptiles (Archelosauria: Crocodylia and Testudines, Rhynchocephalia, and Squamata: Amphisbaenia, Sauria, and Serpentes). The data were gathered from 1288 sources published between 1820 and 2023. The dataset includes morphological, physiological, behavioral, and life history traits, as well as information on the availability of genetic data, IUCN Red List assessments, and population trends. [ABSTRACT FROM AUTHOR]

The Siamese Crocodile Crocodylus siamensis is considered one of the most imperiled and poorly-studied crocodilians in the world. Translocations (reintroductions) - often in conjunction with head-starting of juveniles - are a critical component of efforts to restore viable wild populations of C. siamensis. We here report the first confirmed nesting by a known-age, head-started, and translocated female C. siamensis together with observations of nest attendance and nest-associated fauna based on camera trap imagery. Our observations occurred in the Greater Xe Champhone Wetland Complex (GXCWC) in Savannakhet Province, Lao PDR. GXCWC encompasses 45,000 ha of seasonally inundated natural and anthropogenic wetlands, agricultural ecosystems, scrubland, and forest. While collecting eggs for incubation in May 2022, we were able to identify a unique series of notched tail scutes on a female C. siamensis as she aggressively defended a nest. From these markings we determined the female was hatched on 11 August 2012 (age = 9.75 years) and released in March 2014, approximately 3.5 km from the nest site. A game camera placed at the nest on 11 May 2022 and recovered on 5 July 2022 (34 trap nights) recorded 1724 images. These images indicated the female remained in attendance at the nest throughout the monitoring period. Camera trap imagery captured eight nest repair events and two nest defense events; during the latter the female defended the nest from village dogs. Eleven species of nest-associated fauna were recorded by the game camera, including eight and three species of birds and mammals, respectively. Our observations are the first confirmed nesting by a head-started, translocated female C. siamensis indicating these are effective conservation strategies for restoring wild populations. We also unequivocally established that head-started female C. siamensis are capable of reproducing when nine-years-old. [ABSTRACT FROM AUTHOR]

Simple Summary: We aimed to evaluate the efficacy of nuisance crocodile relocations using passive spatial quantification in Guanacaste, Costs Rica. Nuisance relocated crocodiles and wild crocodiles were fit with Iridium satellite trackers and movements of all individuals were monitored over months. Nuisance relocated crocodiles either returned to the area of nuisance, or potentially attempted to return, in short time frames. These results highlight the need for alternative management strategies. Anthropogenic alterations of the environment have increased, highlighting the need for human–wildlife coexistence and conflict mitigation. Spatial ecology, and the use of passive satellite movement technology in particular, has been used to identify patterns in human–wildlife conflict as a function of shared resources that present potential for dangerous situations. Here, we aim to remotely identify patterns indicative of human–crocodile conflict in Guanacaste, Costa Rica by exploring site fidelity and diverse modes of movement (i.e., land and water) across space between nuisance (relocated) and non-nuisance (wild) crocodiles. Advanced satellite remote sensing technology provided near-constant movement data on individuals at the regional scale. Telonics Iridium SeaTrkr-4370-4 transmitters were used with modified crocodilian fitting. Results indicate that relocated crocodiles exhibited large-scale movements relative to wild crocodiles. Nuisance relocated crocodiles either returned to the area of nuisance or potentially attempted to in short time frames. The results presented here highlight the need for alternative management strategies that facilitate relocation efficacy. [ABSTRACT FROM AUTHOR]

This study adopts a new approach describing palaeohydrology and palaeoclimates based on the interpretation of stable oxygen isotopes (δ18 O p) recorded in fossil crocodilian teeth. They represent an archive of prime interest for tracking freshwater palaeoenvironmental change, applicable to many palaeontological localities in the world: crocodilian teeth are abundant in continental basins and have been widely distributed since their diversification during the Mesozoic; the enamel phosphate is resistant to diagenesis and retains its original isotopic composition over geological timescales; and their δ18 O p mainly relies on that of the crocodilian's home waterbody (δ18 O w), which in turn reflects waterbody types, regional climate, and evaporation conditions. This study presents the first application of this theoretical interpretative model to the Shungura Formation (Lower Omo Valley, Ethiopia), a key witness of the important environmental change in eastern Africa during the Plio-Pleistocene that impacted the evolution of regional faunas, including humans. In this complex and variable environmental context, the δ18 O p of coexisting crocodilians allows for the fingerprinting of the diversity of aquatic environments they had access to at a local scale. This study sheds light on two important results: the δ18 O p of crocodilian teeth (1) indicates stable aquatic environments in the northern Turkana Depression from 2.97 to ca. 2.57 Ma but a decline in local waterbodies diversity after 2.32 Ma, suggesting increasing aridity, and (2) shows, like previous geochemical studies on palaeosols and bivalves in the area, a significant increase in δ18 O w from 2.97 to ca. 1.14 Ma, likely due to the shifting air stream convergence zones between the West African and Indian Summer Monsoons and/or reduced rainfall over the Ethiopian Highlands. [ABSTRACT FROM AUTHOR]

The crocodilians include true crocodiles, alligators, caimans, and gharial, and the trade of crocodilian products is regulated in accordance with the Convention of Wild Fauna and Flora (CITES). Hong Kong does not have her own wild crocodilians; thus, all crocodilians meat available is presumably imported with proper license. Here, we obtained a dataset of cytochrome oxidase I (COI) gene markers of 114 crocodilian meat samples (including frozen and dried crocodilian meat products) available in the contemporary market. We have also validated these barcodes in a phylogenetic approach with other data deposited on the GenBank, and detected 112 samples belonging to four crocodile species Crocodylus siamensis, C. porosus, C. niloticus and Alligator mississippiensis, and 2 samples belonging to snake Malayopython reticulatus. The dataset generated in this study will be useful for further studies including meat inspection, illegal trading, and enhancement of international and local legislations on illegal reptile importation. [ABSTRACT FROM AUTHOR]

Spinosaurids are a highly morphologically specialized clade of large tetanuran theropod dinosaurs, characterized by their proportionally long, narrow snouts and conical teeth with fluted surfaces. The unusual morphology of spinosaurids has been usually compared with modern crocodilians, but distinct differences between them have been reported as well. Here, numerous craniodental characters that are shared by spinosaurids and large, robust phytosaurs often termed as "brachyrostral" forms are reviewed. Phytosaurs are a clade of carnivorous archosauriforms that resemble crocodilians in overall morphology, and as such a similar lifestyle has been inferred for them as well. Although based on preliminary observations, the shared craniodental characters of spinosaurids and "brachyrostral" phytosaurs, including those not shared with crocodilians, raise the possibility that at least some aspects of the lifestyle of these extinct archosauriform clades were more similar to each other rather than to that of crocodilians [ABSTRACT FROM AUTHOR]

Crocodylus acutus is the most widely distributed crocodile in the Neotropics, playing a key role in the ecosystems it inhabits. However, unsustainable use and habitat degradation have depleted its populations across its range. In Colombia, it is classified as Endangered by local authorities, and a legislative framework for its protection has been created, implementing hunting bans and breeding programmes. Successful implementation of these programmes depends on the existence of baseline genetic information, which is currently insufficient for the species. We assess the genetic diversity, phylogeography, and demographic patterns of the American crocodile in Colombia based on three mitochondrial markers (cox1 , cytb , and trnP/trnF/D-Loop) and propose actions for its management and conservation. We processed 33 American crocodile samples from both wild and captive populations and performed genetic variability, phylogenetic, phylogeographical, and neutrality tests, including previously reported sequences. We found evidence of high genetic variability in Colombia, the existence of clearly differentiated mitochondrial phylogenetic clades, and possible human-influenced or stochastic demographic variation events. We propose guidelines for the translocation of American crocodiles based on our findings and present evidence of possible dispersal events in the Caribbean and Magdalena regions. Finally, we suggest the implementation of management units and identify research priorities for future work. [ABSTRACT FROM AUTHOR]

Acoustic communication occurs in all major groups of terrestrial vertebrates, having evolved independently in early clades of mammals, birds, geckos, crocodilians and frogs, about 100–200 MYA. There is little doubt that acoustic communication was used by ancestral therian mammals, but it is ambiguous whether the reconstruction of the root of the mammalian acoustic evolutionary tree includes basal prototherian monotremes. We present here five first‐hand accounts of dove‐like cooing sounds and analyse the acoustics of three vocalization recordings for two observations of wild short‐beaked echidnas (Tachyglossus aculeatus) to quantitatively confirm acoustic communication by this species. The 'cooing' tones were quite distinctive from exhalations, wheezes and grunts, being ~0.044 s down‐sweeps from ~320 to 190 Hz, peaking at ~260 Hz, with at least one harmonic overtone. Tones occurred singly or as doublets, triplets (most common), quadruplets and quintuplets, with the leading tone typically the strongest and most broadband. We conclude that echidnas do produce vocalizations, but they are infrequent and acoustic communication is not their primary mode of communication. This unequivocal evidence for vocalization by short‐beaked echidnas resolves a long‐standing debate concerning the occurrence of acoustic communication by echidnas, which together with well‐documented vocalizations by platypus, support a very early evolution of acoustic communication amongst mammals, pre‐dating at least the common ancestor of monotremes and therian mammals. [ABSTRACT FROM AUTHOR]

The cobra venom factor (CVF) is an unusual non-toxic complement system-activating protein reported in the venom of many family Elapidae snakes, and it is closely related to C3 complement. The archosaurs, including crocodilians, were traditionally considered a completely non-venomous group of animals; however, the identification of some related sequences similar to CVF proteins in the crocodilian genome may trigger important discussions and manage interesting hypotheses. The aim of this work was to identify VF-like protein in Caiman latirostris DNA samples. The results demonstrate the presence of VF-like in C. latirostris and showed a strong homology of VF-like and C3 complement, indicating a probable paralogy between both proteins in crocodilians. Also, these findings provide some potential explanations to justify presence of VF-like protein in crocodilians: one is based on the horizontal transfer of a transposable element from a virus as a vector, and another proposes the horizontal gene transfer by the predator–prey interaction between crocodilians and snakes. Our results are in accordance with investigations that propose the presence of snakes' venom components in non-venomous reptiles. However, more research will be needed to determine if VF-like in crocodilians has a similar function to CVF. [ABSTRACT FROM AUTHOR]

To assess the patterns and severity of disjunction at multiple taxonomic levels for birds, amphibians, crocodilians, and mammals in the western hemisphere, we compiled over 10,100 species ranges and analyzed each range using ERSI ArcMap (10.8.1). After identifying species ranges that were disjunct by 500 km or more, we calculated the mean distance between the disjunct range polygon and primary polygon (d) and relative disjunct area (A) and analyzed disjunction by geographic area and latitude. Birds are the most commonly disjunct taxa (19.3%), followed by mammals (6.4%) and amphibians (2.8%). According to distance and relative area, birds are more severely disjunct than amphibians and mammals. Geographically, South America is home to the largest number of disjunctions across all taxa and latitudinal trends show that disjunction varies by latitude and, coincident with species richness, peaks in the southern tropics. Similarities in disjunction patterns, particularly between mammals and amphibians, suggest that geographic factors, along with dispersal ability, play a key role in creating disjunct distributions. [ABSTRACT FROM AUTHOR]

Simple Summary: The skin of American alligators became lighter when animals were exposed to light colored environments. This change occurred over 2–3 months, and was caused by increased pigmented cells in the dermal layers of the skin. Alligators hatch with bright vertical yellow and black stipes that presumably function as camouflage in emergent vegetation. However, the yellow stripes gradually fade/darken until alligators become a homogenous dark gray/black color as adults. Because alligators live in more temperate climates than other crocodilians, we propose that the loss of yellow stripes might help alligators thermoregulate more efficiently during colder months. We measured the brightness of stripes on wild alligators of a broad spectrum of sizes from three different latitudinal locations within their natural range: northern (South Carolina), central (south Louisiana/southeast Texas), and southern (South Florida). The alligators in South Carolina lost stripes faster as they grew larger, while the alligators in the middle portion of the range became darker at a slower rate, and animals in south Florida lost their stripes at an even slower rate. The loss of stripes at different rates might allow alligators to be more efficient at thermal regulation in the different areas that they inhabit. To assess skin color change in alligators, we maintained animals in differently lighted environments and also measured skin colors in an ontogenetic series of wild animals. Juvenile alligators maintained in black enclosures exhibited a gradual lightening of skin color when shifted to white enclosures, and these observed changes were reversible. A histological examination of the skins of alligators maintained in dark tanks showed that the dermis exhibited a dense layer of pigmented cells, while samples from the same animals in light environments exhibited a more diffuse pigmented layer. As alligators grow, they exhibit an ontogenetic loss of stripes that may aid in crypsis and predation. Hatchlings have intense black and yellow vertical stripes that darken with age; adults are a more homogenous black/gray color. Since alligators live in temperate climates and adults have lower surface area/volume ratios, which can be detrimental for the absorption of radiant energy, the darker color of larger animals may also aid in thermoregulation. Alligators at the northern end of their range, with colder climates, exhibited darker skin tones, and the ontogenetic extinction of stripes occurred at a more accelerated rate compared to animals in southern, warmer regions, supporting the idea that latitude-dependent ontogenetic color shift has a role in thermoregulation. [ABSTRACT FROM AUTHOR]

Reptiles and amphibians are largely present in many environments, including domestic areas when they are kept as pet animals. They often harbor zoonotic pathogens, which can pose a serious risk of infection for humans, mainly immunocompromised individuals, the elderly, children, and pregnant women. Several studies have been carried out to verify the role of cold-blooded animals in the epidemiology of some bacteria, mainly Salmonella, whereas scarce attention has been focused on these animals as a source of staphylococci. These bacteria are often antimicrobial-resistant and they act as opportunistic pathogens, which can cause relevant infections in humans and animals, both domestic and wild. Asymptomatic reptiles and amphibians often harbor staphylococcal strains, such as Staphylococcus aureus and coagulase-negative Staphylococcus spp.; however, these bacteria have been associated with clinical conditions that usually appear in animals under stress conditions. In all cases, greater attention should also be focused on staphylococci in cold-blooded animals due to their implications in human and veterinary medicine.

Acoustic techniques are rapidly becoming powerful tools for species monitoring and biodiversity assessment. These methods can be particularly appropriate for forest-dwelling crocodiles which are difficult to survey visually. However, basic vocal-repertoire data is lacking for many of the poorly known species. Here, we used passive acoustic recorders to capture 97 spontaneous vocal signals from a pair of captive adult African dwarf crocodiles (Osteolaemus tetraspis). We catalogued their acoustic repertoire and compared the calls recorded in captivity with 201 suspected wild O. tetraspis calls recorded in Gabon to determine whether the wild calls belonged to the same species. Captive and wild crocodiles produced the same four types of calls, not previously identified in other crocodylids. Short, low-frequency "drums" (31±12 Hz), longer, low-frequency "rumbles" (40 ± 14 Hz), as well as higher frequency "moos" (299 ± 133 Hz) and "gusts" (219 ± 108 Hz). Our results provide reference for species identification and support implementation of acoustic-based methods for African dwarf crocodile monitoring and conservation assessment. The data can further contribute to landscape-wide biodiversity monitoring and counter-poaching activities, as well as improving our understanding of crocodilian ecology and behaviour. [ABSTRACT FROM AUTHOR]

Efficient locomotion in terrestrial vertebrates relies on intra-limb coordination that emerges through interaction with the environment and passive interlocking of the musculoskeletal system. These structures have been well investigated in some mammals and birds, but the presence of similar structures in other terrestrial vertebrates has been under appreciated. This study addresses the functionality of the passive interlocking system in reptilian hindlimb locomotion by dissecting Crocodylus porosus and constructing a robot. Based on the dissection, we hypothesized that the passive interlocking mechanism consisted of multiple muscles to maintain the semi-erect limb posture and support its weight. The mechanism is provided by the caudifemoralis longus muscle, along with its tendon and the gastrocnemius externus, acting as a passive element that interacts with the ground reaction force. Accordingly, the feasibility of the interlocking function was demonstrated by a robot implementing the hindlimb and pelvic musculoskeletal system of crocodilians. This study provides new insights into the locomotion mechanism of crocodilians and emphasizes the importance of passive interlocking in efficient locomotion in terrestrial vertebrates. The findings could have implications for developing biomimetic robots and understanding the evolution of terrestrial locomotion in vertebrates. [ABSTRACT FROM AUTHOR]

Baru is a genus that includes several large mekosuchine crocodylians from the Oligo‐Miocene of Australia. Here we describe Baru iylwenpeny sp. nov. from a large sample of cranial bones from the Upper Miocene Alcoota Local Fauna of the Northern Territory. Baru iylwenpeny can be diagnosed by several autapomorphies that include, but are not limited to: extreme reduction of the pneumatic foramina associated with the diverticula that invade the bones of the suspensorium; and enlargement of the postcaniniform maxillary teeth resulting in crowding of the postcaniniform alveoli and a reduction in the number of maxillary alveoli to 12. The new species is the geologically youngest known member of the genus. While species of Baru are a ubiquitous component of Oligo‐Miocene crocodylian assemblages from northern Australia, they are absent from all known Plio‐Pleistocene sites, suggesting the extinction of the genus by the latest Miocene. We suggest that the marked taxonomic turnover of crocodylian assemblages between the Upper Miocene Alcoota Local Fauna and the Lower Pliocene is the result of a short period of severe aridity during the latest Miocene, causing widespread crocodylian extinctions across Australia, followed by the establishment of taxonomically novel crocodylian faunas in the Pliocene. This event mirrors similar contemporary losses of crocodylian diversity in Africa and South America, although these cases are partly driven by local tectonic events. It is likely that late Cenozoic global cooling also played a role in these extinctions. [ABSTRACT FROM AUTHOR]

The evolution of nest site use and nest architecture in the non-avian ancestors of birds remains poorly understood because nest structures do not preserve well as fossils. Nevertheless, the evidence suggests that the earliest dinosaurs probably buried eggs below ground and covered them with soil so that heat from the substrate fuelled embryo development, while some later dinosaurs laid partially exposed clutches where adults incubated them and protected them from predators and parasites. The nests of euornithine birds—the precursors to modern birds—were probably partially open and the neornithine birds—or modern birds—were probably the first to build fully exposed nests. The shift towards smaller, open cup nests has been accompanied by shifts in reproductive traits, with female birds having one functioning ovary in contrast to the two ovaries of crocodilians and many non-avian dinosaurs. The evolutionary trend among extant birds and their ancestors has been toward the evolution of greater cognitive abilities to construct in a wider diversity of sites and providing more care for significantly fewer, increasingly altricial, offspring. The highly derived passerines reflect this pattern with many species building small, architecturally complex nests in open sites and investing significant care into altricial young. This article is part of the theme issue 'The evolutionary ecology of nests: a cross-taxon approach'. [ABSTRACT FROM AUTHOR]

This study adopts a new approach describing paleohydrology and paleoclimates based on the interpretation of stable oxygen isotopes (δ18Op) recorded in fossil crocodilian teeth. They represent an archive of prime interest for tracking freshwater paleoenvironmental change, applicable for many paleontological localities in the world: crocodilian teeth are abundant in continental basins and widely distributed since their diversification during the Mesozoic; the enamel phosphate is resistant to diagenesis and retains its original isotopic composition over geological timescales; their δ18Op mainly relies on that of the crocodilian's home water body (δ18Ow), which in turn reflects water body types, regional climate, and evaporation conditions. This study presents the first application of this interpretative model to the Shungura Formation (Lower Omo Valley, Ethiopia), a key witness of the important environmental changes in eastern Africa during the Plio-Pleistocene that impacted the evolution of regional faunas, including humans. In this complex and variable environmental context, the δ18Op of coexisting crocodilians allows for fingerprinting the diversity of aquatic environments they had access to at a local scale. Like previous geochemical studies performed on paleosols and bivalves in this area, our data indicate a marked increase in δ18Ow between 2.97 Ma and ca. 1.14 Ma, probably resulting from the joint effect of the migration of the air streams convergence zones between the West African and Indian Summer Monsoons and of the decrease in rainfall amounts above the Ethiopian Highlands. Contrary to some conclusions based on terrestrial proxies, the δ18Op of crocodilian teeth does highlight any major change affecting aquatic environments, rather pointing to stability of these environments between 2.97 Ma and ca. 2.57 Ma. By contrast, the diversity of aquatic environments accessible to crocodilians seems to be restricted in most analysed stratigraphical units after ca. 2.32 Ma, a feature that may reflect more arid conditions in the Turkana Depression. [ABSTRACT FROM AUTHOR]

Plasma biochemistry values represent a crucial and minimally invasive tool for evaluating nutritional and physiological condition of the animal. Biochemical data provides valuable information in those species exposed to environmental stressors. In this study, we aimed to apply for the first time micro‐volume plasma tests to measured total plasma protein, albumin, and glucose in juvenile Caiman latirostris and to compare our results with other studies reporting crocodilian biochemistry values. We found that caimans from heat treatment were heavier, longer and had higher levels of glucose than those from the control group. Conversely, food restricted caimans had less growth, body condition and had 32.1% lower albumin concentrations than those from the control group. While no significant differences were observed in any parameters measured from water restricted caimans compared with control group. The values obtained for each of the biochemical determinations were lower than those previously reported for adult of C. latirostris, but similar finding for protein concentration compared with Alligator mississippiensis. Micro technique offers the advantage of increasing information and at the same time a greater physiological understanding of the crocodilians species. Research highlights: This is the first report that apply micro technique for measured biochemical analytes of plasma of juvenile Caiman latirostris.Total protein, albumin and glucose concentrations in juvenile caimans were lower than those previously reported for adults of Caiman latirostris. [ABSTRACT FROM AUTHOR]

Background: Crocodile farming aims to produce high-quality skins from captive crocodilians. Captivity usually exposes the animals to stressful conditions, resulting in increased serum corticosterone (CORT) levels that correlate negatively with those of sex hormones and reproductive success. Objective: To evaluate serum concentrations of CORT and sex hormones and their relationship in farmed Morelet's crocodiles (Crocodylus moreletii) during the non-breeding (NBS) and breeding (BS) seasons. Methods: The study included 59 adult crocodiles (29 females and 30 males). One blood sample was collected in NBS (n=31) and BS (n=28) from each crocodile to determine serum concentrations of CORT, estradiol (E2), progesterone (P4), and testosterone (T). Crocodiles were kept in mixed-sex groups and were fed once or twice a week throughout the study. Results: In females, CORT was higher in NBS (p<0.05) but had no correlation with E2 or P4 in any season (p>0.05). In males, CORT was similar in NBS and BS (p>0.05) and had no correlation with T (p>0.5). Conclusion: The CORT levels had no effect on sex hormones. This could be explained by low CORT levels resulting from farming conditions where the animals were not exposed to severe or chronic stress. [ABSTRACT FROM AUTHOR]

The independent origins of middle ears in testudinates, lepidosaurs, and archosaurs in the Triassic led to lineage-specific developments in their auditory epithelia. In comparison to the inferred ancestral state, little changed in testudinates, but archosaurs and most lepidosaurs evolved longer, differentiated auditory papillae. In archosaurs, sensory hair cells specialized across and along the papillae, resulting in mainly sensory tall hair cells and mainly mechanically active short hair cells. Crocodilians have 5 mm-long papillae, but relatively low upper frequency limits at around 4 kHz. Avian papillae are mostly 3 to 5 mm in length, being shorter in small species; in owls they exceptionally reach almost 12 mm and have an upper limit of above 10 kHz. Lepidosaurs retained the ancestral papilla as a low-frequency responsive area with one type of hair cell, but most added newly evolved areas (of max. 2 mm length) consisting of oppositely oriented hair cells responding to frequencies above 1 kHz. Initially, these areas flanked both ends of the ancestral area and were redundant in their responses to sound. The evolution of specific configurations in most families eliminated this redundancy, but the paths taken resulted in diverse anatomies that show high degrees of family specificity. Despite these differences, the high-frequency hearing limit of lepidosaurs rarely exceeds 5 kHz. [ABSTRACT FROM AUTHOR]

We present the first detailed braincase anatomical description and neuroanatomical study of Portugalosuchus azenhae, from the Cenomanian (Late Cretaceous) of Portugal. This eusuchian crocodylomorph was originally described as a putative Crocodylia and one of the oldest representatives of this clade; however, its phylogenetic position remains controversial. Based on new data obtained from high resolution Computed Tomography images (by micro‐CT scan), this study aims to improve the original description of this taxon and also update the scarce neuroanatomical knowledge of Eusuchia and Crocodylia from this time interval, a key period to understand the origin and evolution of these clades. The resulting three‐dimensional models from the CT data allowed a detailed description of its well‐preserved neurocranium and internal cavities. Therefore, it was possible to reconstruct the cavities of the olfactory region, nasopharyngeal ducts, brain, nerves, carotid arteries, blood vessels, paratympanic sinus system and inner ear, which allowed to estimate some neurosensorial capabilities. By comparison with other crocodylomorphs, these analyses showed that Portugalosuchus, back in the Cenomanian, already displayed an olfactive acuity, sight, hearing and cognitive skills within the range of that observed in other basal eusuchians and crocodylians, including extant species. In addition, and in order to test its disputed phylogenetic position, these new anatomical data, which helped to correct and complete some of the original observations, were included in one of the most recent morphology‐based phylogenies. The position of Portugalosuchus differs slightly from the original publication since it is now located as a "thoracosaurid" within Gavialoidea, but still as a crocodylian. Despite all this, to better contrast these results, additional phylogenetic analyses including this new morphological character coding together with DNA data should be performed. [ABSTRACT FROM AUTHOR]

The phylogenetic relationships within crown Crocodylia remain contentious due to conflicts between molecular and morphological hypotheses. However, morphology‐based datasets are mostly constructed on external characters, overlooking internal structures. Here, we use 3D geometric morphometrics to study the shape of the intertympanic sinus system in crown crocodylians during ontogeny, in order to assess its significance in a taxonomic context. Intertympanic sinus shape was found to be highly correlated with size and modulated by cranial shape during development. Still, adult sinus morphology distinguishes specimens at the family, genus and species level. We observe a clear distinction between Alligatoridae and Longirostres, a separation of different Crocodylus species and the subfossil Malagasy genus Voay, and a distinction between the Tomistoma and Gavialis lineages. Our approach is independent of molecular methods but concurs with the molecular topologies. Therefore, sinus characters could add significantly to morphological datasets, offering an alternative viewpoint to resolve problems in crocodylian relationships. [ABSTRACT FROM AUTHOR]

Herein, we report a small collection of isolated crocodilian teeth recovered from shallow marine Eocene deposits of Turnu Rou (Porceti), Romania. The teeth probably represent an attritional assemblage that could have belonged to several individuals of various sizes and ages, provided with heterodont dentition of at least five morphotypes (slender caniniform, triangular-lanceolate shaped, enlarged conical, slender conical, and low crowned). We assigned the isolated teeth to Gavialoidea based on a number of morphological characters shared with representatives of early gavialoids, known from the early-middle Eocene of western Europe or North Africa. The gavialoids from Turnu Rou represent a new group for the Paleogene of Romania that probably reached the territory of southern Transylvania in the Middle Eocene. Possible scenarios for the origin of southern Transylvanian gavialoids imagine an existence of a western-eastern European route or a migration route direct from North Africa and an ancestor close to the morphology of Maroccosuchus from the region of western Tethys. [ABSTRACT FROM AUTHOR]

Crocodylians are top predators that play key ecological roles in aquatic ecosystems. As in other groups of large predators, crocodylian populations are often impacted by habitat loss, habitat degradation or direct exploitation for commercial purposes or subsistence. Hence, understanding their spatiotemporal ecology can provide valuable information for conservation planning. We reviewed the published scientific literature on telemetry-tracking in crocodylians, combining the terms "telemetry", "track" or "tag" and variations; "VHF", "UHF", "satellite", "GPS", "radio", "acoustic" or "transmitters"; and "caiman", "alligator", "crocodile", "gharial" or "Crocodylia". Publications retrieved by our search were carefully reviewed for information on study length, geographic location, sample size, taxonomy, and telemetry technology used. We identified 72 research articles in indexed journals and 110 reports available from the IUCN's Crocodile Specialist Group, published between 1970 and 2022. Publications included 23 of the 27-living described crocodylian species. We identified strong geographic and taxonomic biases, with most articles proceeding from the USA (21.2%) and Australia (14%), with Alligator mississipiensis and Crocodylus porosus as the main target species in studies conducted in these countries, respectively. Despite representing 22% of IUCN's reports, Gavialis gangeticus was referred in a single indexed research article. VHF telemetry was the prevalent tracking method, followed by GPS and acoustic transmitters. Studies using VHF devices had generally shorter in length when compared to alternative technologies. Transmitter weight represented less than 2% of the body mass of the carrying individual in all studies. Although attachment site of transmitters was notified in all research papers, few described anaesthetic or clinical procedures during attachment (33%). Our review highlights the need to encourage publication of crocodylian telemetry studies in non-English speaking countries in Asia, Africa, and Latin America, where many endemic species are threatened. We also highlight the need of detailed information on methods and results to facilitate the choice and implementation of appropriate protocols in future telemetry-tracking studies. [ABSTRACT FROM AUTHOR]

Simple Summary: Due to their significant size and aggressiveness, the capture of adult crocodiles carries significant risk, both in terms of stress and injuries to themselves and to operators. Neuromuscular blocking agents act by inducing flaccid muscle paralysis, thereby reducing the physical and chemical risks associated with transportation and anesthesia. Pancuronium bromide and its antagonist, neostigmine methylsulfate, have been successfully used in juvenile and subadult saltwater crocodiles (Crocodylus porosus), but their applications in larger animals (body weight > 230 kg or total length > 3.8 m) or in Nile crocodiles (Crocodylus niloticus) have never been described. We trialed a dose recommendation in nine Nile crocodiles using pancuronium bromide that was originally established for small- and medium-sized saltwater crocodiles, the effect of which can be reversed using neostigmine. We found that the recommended dose caused a prolonged recovery time in adult male Nile crocodiles, and we propose a weight-independent dose for Nile crocodiles with body weight ≥ 300 kg or total length ≥ 4.0 m, which we successfully trialed in 32 animals. (1) Background: Pancuronium bromide is a neuromuscular blocker used for immobilizing crocodiles that can be reversed with neostigmine. A recommended drug dose has only been established for saltwater crocodiles (Crocodylus porosus), mostly based on trials in juveniles and subadults. After trialing a dose recommendation in a small cohort of nine Nile crocodiles (Crocodylus niloticus), we developed and applied a new dose recommendation for large adult Nile crocodiles. (2) Methods: we trialed and adapted a pancuronium bromide (Pavulon 4 mg/2 mL) dose in Nile crocodiles originally established for saltwater crocodiles and applied the new dose for the immobilization of 32 Nile crocodiles destined for transport. Reversal was achieved with neostigmine (Stigmine 0.5 mg/mL). (3) Results: Nine crocodiles were included in the trial phase; the induction time was highly variable (average: 70 min; range: 20–143 min), and the recovery time was prolonged (average: 22 h; range: 50 min–5 days), especially in large animals after reversal with neostigmine. Based on these results, we established a dose-independent recommendation (3 mg pancuronium bromide and 2.5 mg neostigmine) for animals weighing ≥ 270 kg (TL ≥ ~3.8 m). When applied to 32 adult male crocodiles (BW range: 270–460 kg; TL range: 3.76–4.48 m), the shortest induction time was ~20 min and the longest ~45 min. (4) Conclusions: Pancuronium bromide and its antidote, neostigmine, are effective for the immobilization and reversal of adult male Nile crocodiles (TL ≥ 3.8 m or BW ≥ 270 kg) when given in a weight-independent fashion. [ABSTRACT FROM AUTHOR]

The vertebrate trigeminal nerve is the primary mediator of somatosensory information from nerve endings across the face, extending nerve branches through bony canals in the face and mandibles, terminating in sensory receptors. Reptiles evolved several extreme forms of cranial somatosensation in which enhanced trigeminal tissues are present in species engaging in unique mechanosensory behaviors. However, morphology varies by clade and ecology among reptiles. Few lineages approach the extreme degree of tactile somatosensation possessed by crocodylians, the only remaining members of a clade that underwent an ecological transition from the terrestrial to semiaquatic habitat, also evolving a specialized trigeminal system. It remains to be understood how trigeminal osteological correlates inform how adaptations for enhanced cranial sensation evolved in crocodylians. Here we identify an increase in sensory abilities in Early Jurassic crocodylomorphs, preceding the transitions to a semiaquatic habitat. Through quantification of trigeminal neurovascular canal branching patterns in an extant phylogenetic bracket we quantify and identify morphologies associated with sensory behaviors in representative fossil taxa, we find stepwise progression of increasing neurovascular canal density, complexity, and distribution from the primitive archosaurian to the derived crocodilian condition. Model‐based inferences of sensory ecologies tested on quantified morphologies of extant taxa with known sensory behaviors indicate a parallel increase in sensory abilities among pseudosuchians. These findings establish patterns of reptile trigeminal ecomorphology, revealing evolutionary patterns of somatosensory ecology. [ABSTRACT FROM AUTHOR]

Background: Crocodile farming aims to produce high-quality skins from captive crocodilians. Captivity usually exposes the animals to stressful conditions, resulting in increased serum corticosterone (CORT) levels that correlate negatively with those of sex hormones and reproductive success. Objective: To evaluate serum concentrations of CORT and sex hormones and their relationship in farmed Morelet’s crocodiles (Crocodylus moreletii) during the non-breeding (NBS) and breeding (BS) seasons. Methods: The study included 59 adult crocodiles (29 females and 30 males). One blood sample was collected in NBS (n=31) and BS (n=28) from each crocodile to determine serum concentrations of CORT, estradiol (E2), progesterone (P4), and testosterone (T). Crocodiles were kept in mixed-sex groups and were fed once or twice a week throughout the study. Results: In females, CORT was higher in NBS (p0.05). In males, CORT was similar in NBS and BS (p>0.05) and had no correlation with T (p>0.5). Conclusion: The CORT levels had no effect on sex hormones. This could be explained by low CORT levels resulting from farming conditions where the animals were not exposed to severe or chronic stress.

The visual ecology of early mammals remains poorly resolved. Studies of ancestral photopigments suggest an ancient transition from nocturnal to more crepuscular conditions. By contrast, the phenotypic shifts following the split of monotremes and therians—which lost their SWS1 and SWS2 opsins, respectively—are less clear. To address this, we obtained new phenotypic data on the photopigments of extant and ancestral monotremes. We then generated functional data for another vertebrate group that shares the same photopigment repertoire as monotremes: the crocodilians. By characterizing resurrected ancient pigments, we show that the ancestral monotreme underwent a dramatic acceleration in its rhodopsin retinal release rate. Moreover, this change was likely mediated by three residue replacements, two of which also arose on the ancestral branch of crocodilians, which exhibit similarly accelerated retinal release. Despite this parallelism in retinal release, we detected minimal to moderate changes in the spectral tuning of cone visual pigments in these groups. Our results imply that ancestral forms of monotremes and crocodilians independently underwent niche expansion to encompass quickly changing light conditions. This scenario—which accords with reported crepuscular activity in extant monotremes—may help account for their loss of the ultraviolet-sensitive SWS1 pigment but retention of the blue-sensitive SWS2. [ABSTRACT FROM AUTHOR]

Three ichnospecies of the Late Jurassic trace fossil genus Rhamphichnus were first described and interpreted as the walking tracks of non-pterodactyloid pterosaurs like Rhamphorhynchus. This despite not resembling any previously identified pterosaur tracks and having a morphology unmatched by pterosaur skeletal elements. To fit the pterosaurian model, elongated imprints of R. pereiraensis and R. lafaurii , displaying four or five digit impressions were interpreted as manus prints, while shorter, five-digit prints were interpreted as imprints made by pedes with dislocated metatarsals and disarticulated phalanges. Comparison of published images and descriptions of Rhamphichnus ispp. to skeletal elements of six contemporaneous non-pterodactyloid taxa, skeletons and tracks from pterodactyloid pterosaurs, and modern and ancient lepidosaurs and crocodilians suggests an alternative interpretation. R. crayssacensis closely resembles crocodilian (Crocodylopodus (Sustenodactylus) isp.) and crocodylomorph (Batrachopus isp.) tracks; its holotype trackway was found 50 cm away from and parallel to a crocodilian swimming trackway with the same sized feet, possibly made by the same individual. R. pereiraensis and R. lafaurii strongly resemble lepidosaurian tracks and match the size and morphology of contemporary rhynchocephalians. Prints originally interpreted as manual and pedal in R. pereiraensis and R. lafaurii are reinterpreted and transposed in light of new data from pterosaurian, lepidosaurian, and crocodilian tracks and anatomy. Identification of fossil trackmakers depends on comparisons of a wide range of candidate taxa and elimination of those that cannot be considered further. With this reinterpretation of Rhamphichnus , there are no non-pterodactyloid pterosaurian tracks yet identified in the fossil record. [ABSTRACT FROM AUTHOR]

Isolated teeth, previously referred to Aves, are more common than other bird fossils from the Late Cretaceous of Alberta. However, there are no known morphological synapomorphies that distinguish isolated bird teeth, and features of these teeth are generally shared with those of non-avian theropods and crocodilians. Here, specimens ranging from Late Santonian to Late Maastrichtian in age are described and qualitatively categorized into morphotypes, most of which strongly resemble teeth of extant juvenile and some fossil crocodilians. Variation within this sample of teeth may therefore reflect the heterodont dentition of crocodilians, rather than avian species diversity. Quantitative analysis Principal Component Analysis was mostly uninformative, with limited overlap between putative avian teeth and those of known Cretaceous birds, crocodilians, and non-avian theropods. The reassignment of these putative avian teeth to Crocodylia has important ramifications for our understanding of the evolutionary history of Cretaceous birds. [ABSTRACT FROM AUTHOR]

The Anthropocene is tightly associated with a drastic loss of species worldwide and the disappearance of their key ecosystem functions. The orders Testudines (turtles and tortoises) and Crocodilia (crocodiles, alligators, and gharials) contain numerous threatened, long-lived species for which the functional diversity and potential erosion by anthropogenic impacts remains unknown. Here, we examine 259 (69%) of the existing 375 species of Testudines and Crocodilia, quantifying their life history strategies (i.e., trade-offs in survival, development, and reproduction) from open-access data on demography, ancestry, and threats. We find that the loss of functional diversity in simulated extinction scenarios of threatened species is greater than expected by chance. Moreover, the effects of unsustainable local consumption, diseases, and pollution are associated with life history strategies. In contrast, climate change, habitat disturbance, and global trade affect species independent of their life history strategy. Importantly, the loss of functional diversity for threatened species by habitat degradation is twice that for all other threats. Our findings highlight the importance of conservation programmes focused on preserving the functional diversity of life history strategies jointly with the phylogenetic representativity of these highly threatened groups. Many species of reptiles are threatened with extinction. This analysis on 259 species of turtles, tortoises and crocodilians identifies anthropogenic threats that disproportionally affect species with certain life history strategies and others that affect all species similarly. [ABSTRACT FROM AUTHOR]

Eggshell morphology is a valuable indicator of the local conditions within the nests of modern crocodilians and birds. In contrast to these latter, the anatomical structure of the eggshells of most crocodilian species is practically unknown. Here, we provide the first characterization of crocodilian eggshells, using x-ray micro-CT scans. We studied eggshells of Caiman latirostris and Caiman yacare from various developmental stages that coincide with the beginning of embryonic ossification. The new 3D renderings revealed complex ornamentation, unique among crocodilians, and amphora-shaped pore canals, some of which converge in single pore openings. We also documented a high density of pore canals with a gas diffusion capacity 45 times higher than the average predicted for modern avian eggshells. The external ornamentation and the thickness of the compact layer of the eggshells (i.e. excluding ornamentation) showed ontogenetic and interspecific differences that could be related to nesting materials and nesting areas selected by each species. The shell features described here evidence a greater structural complexity than previously recognized in phylogenetically close, sympatric crocodilian species. Further comprehensive morphological analyses on other modern and fossil crocodilian eggshells using micro-CT technology will shed new light on the evolution of reproductive strategies in this intriguing archosaur clade. [ABSTRACT FROM AUTHOR]

The genus Caiman is one of the most taxonomically conflicted among crocodilians. Caiman crocodilus has four subspecies: Caiman crocodilus crocodilus , Caiman crocodilus fuscus , Caiman crocodilus chiapasius and Caiman crocodilus apaporiensis , but some studies recognize Caiman yacare as a subspecies of C. crocodilus or as a C. crocodilus–C. yacare complex. In Argentina, Caiman latirostris and C. yacare are present and included in sustainable use programmes, although they have hardly been studied at the genetic level. The present study had two main objectives: (1) to study the genetic diversity, structure and phylogeny of C. yacare and C. latirostris in Argentina; and (2) to perform a phylogenetic analysis of the genus Caiman throughout its entire distribution. The results show high haplotype diversity for both species but low nucleotide diversity for C. latirostris. Phylogenetic analysis shows a clear separation between both species but, surprisingly, a well-differentiated clade belonging to the Chaco region was observed. The phylogenetic analysis exhibited clades made up of the sequences of each Caiman species, with some inconsistencies: in the clade of C. crocodilus , one sequence of C. yacare is included, and one clade is observed including sequences from C. c. fuscus and C. c. chiapasius. These data indicate the need to undertake interdisciplinary studies to clarify the taxonomic status of these crocodilian species. [ABSTRACT FROM AUTHOR]

The earliest Crocodylia from Asia have been represented so far only by alligatoroids and planocraniids. Although definitive crocodyloids are not known until the late Eocene, it has been hypothesized that Asiatosuchus -like basal crocodyloids originated in Asia before the late Palaeocene. In this paper, we describe a new fossil crocodyloid from the lower Palaeocene of Qianshan Basin, Anhui Province, China. The skull and lower jaw fragment exhibit several characteristics typical of juvenile crocodylians. They also display a combination of features not seen in any other taxon, warranting the erection of a new species and genus, Qianshanosuchus youngi gen. & sp. nov. Its affinities are tested in phylogenetic analyses based on two recent character matrices of Eusuchia. To assess the effect of juvenile characteristics on the outcome of the phylogenetic analyses, juvenile specimens of extant crocodylian taxa are analysed in the same way, showing that the effect of their ontogenetic stage on their placement in the tree is minimal. Our analyses point to a basal crocodyloid position for Q. youngi. With these findings, the presence of Crocodyloidea in Asia is extended to the early Palaeocene, 15–20 Myr earlier than formerly thought. Furthermore, our results corroborate previous hypotheses of a Palaeocene dispersal route of Asiatosuchus -like crocodyloids from Asia into Europe. [ABSTRACT FROM AUTHOR]