Search

A new ankylosaurid dinosaur,Tarchia tumanovaesp. nov., has been recovered from the Upper Cretaceous Nemegt Formation of Mongolia. It includes a well-preserved skull, dorsal, sacral, caudal vertebrae, sixteen dorsal ribs, ilia, a partial ischium, free osteoderms, and a tail club. The squamosal horns ofT. tumanovaeare divided into two layers, the external dermal layer and the underlying squamosal horn proper. The irregular ventral margin of the base of the upper dermal layer may represent a resorption surface, suggesting that the squamosal horns of some ankylosaurids underwent extreme ontogenetic remodeling. Localized pathologies on the dorsosacral ribs and the tail provide evidence of agonistic behaviour. The tail club knob asymmetry ofT. tumanovaeresulted from restricted bone growth due to tail club strikes. Furthermore,T. tumanovaehad an anteriorly protruded shovel-shaped beak, which is a morphological character of selective feeders. Ankylosaurid diets shifted from low-level bulk feeding to selective feeding during the Baruungoyot and the Nemegt “age” (middle Campanian-lower Maastrichtian). This ankylosaurid niche shifting might have been a response to habitat change and competition with other bulk-feeding herbivores.

A braincase of the Cretaceous titanosaurian sauropod Malawisaurus dixeyi, complete except for the olfactory region, was CT scanned and a 3D rendering of the endocast and inner ear was generated. Cranial nerves appear in the same configuration as in other sauropods, including derived features that appear to characterize titanosaurians, specifically, an abducens nerve canal that passes lateral to the pituitary fossa rather than entering it. Furthermore, the hypoglossal nerve exits the skull via a single foramen, consistent with most titanosaurians, while other saurischians, including the basal titanosauriform, Giraffatitan, contain multiple rootlets. The size of the vestibular labyrinth is smaller than in Giraffatitan, but larger than in most derived titanosaurians. Similar to the condition found in Giraffatitan, the anterior semicircular canal is larger than the posterior semicircular canal. This contrasts with more derived titanosaurians that contain similarly sized anterior and posterior semicircular canals, congruent with the interpretation of Malawisaurus as a basal titanosaurian. Measurements of the humerus of Malawisaurus provide a body mass estimate of 4.7 metric tons. Comparison of body mass to radius of the semicircular canals of the vestibular labyrinth reveals that Malawisaurus fits the allometric relationship found in previous studies of extant mammals and Giraffatitan brancai. As in Giraffatitan, the anterior semicircular canal is significantly larger than is predicted by the allometric relationship suggesting greater sensitivity and slower movement of the head in the sagittal plane.

The separation of Africa from South America and the growth of the South Atlantic are recorded in rocks exposed along the coast of Angola. Tectonic processes that led to the formation of Africa as a continent also controlled sedimentary basins that preserve fossils. The vertebrate fossil record in Angola extends from the Triassic to the Holocene and includes crocodylomorph, dinosaur, and mammaliamorph footprints, but more extensively, bones of fishes, turtles, plesiosaurs, mosasaurs, crocodiles, and cetaceans. Pterosaurs, dinosaurs, and land mammals are rare in Angola. The northward drift of Africa through latitudinal climatic zones provides a method for comparing predicted paleoenvironmental conditions among localities in Angola, and also allows comparison among desert and upwelling areas in Africa, South America, and Australia. South America has shown the least northward drift and its Atacama Desert is the oldest coastal desert among the three continents. Africa’s northward drift caused the displacement of the coastal desert to the south as the continent moved north. Australia drifted from far southerly latitudes and entered the climatic arid zone in the Miocene, more recently than South America or Africa, but in addition, a combination of its drift, continental outline, a downwelling eastern boundary current, the Pacific Ocean to Indian Ocean throughflow, and monsoon influence, make Australia unique.

Derived members of the enigmatic mammalian order Desmostylia have molars comprising appressed columns whose morphology does not render their function in feeding simple to discern. Here we describe a new genus and species, Ounalashkastylus tomidai, more derived than Cornwallius but less derived than Desmostylus and Vanderhoofius, which develop a hypertrophied medial eminence on the dentary ontogenetically. Tooth morphology, vaulted palate and the medial eminence, which can rise to the level of the occlusal surface of M2, suggest that derived desmostylids clenched their teeth strongly while employing suction during feeding, most likely on marine and coastal plants.

Stable oxygen isotope values of inoceramid marine bivalve shells recovered from Bentiaba, Angola, are utilised as a proxy for paleotemperatures during the Late Cretaceous development of the African margin of the South Atlantic Ocean. The δ18O values derived from inoceramids show a long-term increase from –3.2‰ in the Late Turonian to values between –0.8 and –1.8‰ in the Late Campanian. Assuming a constant oceanic δ18O value, an ∼2‰ increase may reflect cooling of the shallow marine environment at Bentiaba by approximately 10°. Bentiaba values are offset by about +1‰ from published records for bathyal Inoceramus at Walvis Ridge. This offset in δ18O values suggests a temperature difference of ∼5° between coastal and deeper water offshore Angola. Cooler temperatures implied by the δ18O curve at Bentiaba coincide with the stratigraphic distribution of diverse marine amniotes, including mosasaurs, at Bentiaba.

We report here new and the first mammaliamorph tracks from the Early Cretaceous of Africa. The tracksite, that also bears crocodylomorph and sauropod dinosaurian tracks, is in the Catoca diamond mine, Lunda Sul Province, Angola. The mammaliamorph tracks have a unique morphology, attributed to Catocapes angolanus ichnogen. et ichnosp. nov. and present an anterolateral projection of digit I and V. The tracks with an average length of 2.7 cm and width of 3.2 cm are the largest mammaliamorph tracks known from the Early Cretaceous unmatched in size in the skeletal fossil record. The crocodylomorph trackways and tracks are attributed to Angolaichnus adamanticus ichnogen. et ichnosp. nov. (‘ichnofamily’ Batrachopodidae) and present a functionally pentadactyl pes, an extremely outwardly rotated handprint, and an unusual tetradactyl and plantigrade manus. One medium-sized sauropod dinosaur trackway preserved skin impressions of a trackmaker with stride length of 1.6 m; a second is that of a small-sized sauropod trackmaker with a pace length of 75 cm.

International audience; Synapsida, the clade including therapsids and thus also mammals, is one of the two major branches of amniotes. Organismal design, with modularity as a concept, offers insights into the evolution of therapsids, a group that experienced profound anatomical transformations throughout the past 270 Ma, eventually leading to the evolution of the mammalian bauplan. However, the anatomy of some therapsid groups remains obscure. Gorgonopsian braincase anatomy is poorly known and many anatomical aspects of the brain, cranial nerves, vasculature, and osseous labyrinth, remain unclear. We analyzed two gorgonopsian specimens, GPIT/RE/7124 and GPIT/RE/7119, using propagation phase contrast synchrotron micro- computed tomography. The lack of fusion between many basicranial and occipital bones in GPIT/RE/7124, which is an immature specimen, allowed us to reconstruct its anatomy and ontogenetic sequence, in comparison with the mature GPIT/RE/7119, in great detail. We explored the braincase and rendered various skull cavities. Notably, we found that there is a separate ossification between what was previously referred to as the ``parasphenoid'' and the basioccipital. We reinterpreted this element as a posterior ossification of the basisphenoid: the basipostsphenoid. Moreover, we show that the previously called ``parasphenoid'' is in fact the co-ossification of the dermal parasphenoid and the endochondral basipresphenoid. In line with previous descriptions, the anatomy of the osseous labyrinth is rendered in detail, revealing a unique discoid morphology of the horizontal semicircular canal, rather than toroidal, probably due to architectural constraints of the ossification of the opisthotic and supraoccipital. In addition, the orientation of the horizontal semicircular canal suggests that gorgonopsians had an anteriorly tilted alert head posture. The morphology of the brain endocast is in accordance with the more reptilian endocast shape of other non-mammaliaform neotherapsids

This publication results from Projecto PaleoAngola, an international cooperative research effort among the contributing authors and their institutions, funded by the National Geographic Society, the Petroleum Research Fund of the American Chemical Society, Sonangol E.P., Esso Angola, Fundacao Vida of Angola, LS Films, Maersk, Damco, Safmarine, ISEM at SMU, The Royal Dutch Embassy in Luanda, TAP Airlines, Royal Dutch Airlines, The Saurus Institute, and the Perot Museum of Nature and Science. JS was additionally funded by Yale University and the Alfred Kordelin Foundation. We dedicate this contribution to the late Kalunga Lima, our friend and colleague in Projecto PaleoAngola. We thank Margarida Ventura and Andre Buta Neto for providing our team help in the field. Tako and Henriette Koning provided valuable support and friendship in Angola. We thank Tyrone Rooney of Michigan State University for XRF examination on the Ombe basalt. We present the δ13C and paleomagnetic stratigraphy for marine strata at the coast of southern Angola, anchored by an intercalated basalt with a whole rock 40Ar/39Ar radiometric age of 84.6 ± 1.5 Ma, being consistent with both invertebrate and vertebrate biostratigraphy. This is the first African stable carbon isotope record correlated to significant events in the global carbon record spanning the Late Cenomanian to Early Maastrichtian. A positive ~3% excursion seen in bivalve shells below the basalt indicates the Cenomanian-Turonian Boundary Event at 93.9 Ma, during Oceanic Anoxic Event 2. Additional excursions above the basalt are correlated to patterns globally, including a negative ~3% excursion near the top of the section interpreted as part of the Campanian-Maastrichtian Boundary Events. The age of the basalt ties the studied Bentiaba section to a pulse of Late Cretaceous magmatic activity around the South Atlantic and significant tectonic activity, including rotation, of the African continent. publishersversion published

New elasmosaurid plesiosaur specimens are described from the Early Maastrichtian of Angola. Phylogenetic analyses reconstruct the Angolan taxon as an aristonectine elasmosaurid and the sister taxon of an unnamed form of similar age from New Zealand. Comparisons also indicate a close relationship with an unnamed form previously described from Patagonia. All of these specimens exhibit an ostensibly osteologically immature external morphology, but histological analysis of the Angolan material suggests an adult with paedomorphic traits. By extension, the similarity of the Angolan, New Zealand and Patagonian material indicates that these specimens represent a widespread paedomorphic yet unnamed taxon.

Mosasaurs are marine squamates with a 32.5. million-year history from their appearance at 98. Ma to their extinction at the K-Pg boundary (65.5. Ma). Using a database of 43 generic and 94 species-level taxa, we compare the taxonomic diversity and patterns of morphological disparity in mosasaurs with sea level, sea surface temperature, and stable carbon isotope curves for the Upper Cretaceous to explore factors that may have influenced their evolution. No single factor unambiguously accounts for all radiations, diversification, and extinctions; however, the broader patterns of taxonomic diversification and morphological disparity point to niche differentiation in a "fishing up" scenario under the influence of "bottom-up" selective pressures. The most likely driving force in mosasaur evolution was high productivity in the Late Cretaceous, driven by tectonically controlled sea levels and climatically controlled ocean stratification and nutrient delivery. When productivity collapsed at the end of the Cretaceous, coincident with bolide impact, mosasaurs became extinct. © 2013 Elsevier B.V.

We report here the addition of two rare mosasaur taxa to the Maastrichtian marine amniote fauna of Angola, both of which are also found in northern Europe. The new specimens include a dentary fragment referable to the large carnivorePrognathodoncf.saturatorand an isolated tooth of the small durophageCarinodens belgicus. Both were recovered from Maastrichtian outcrops in southern Angola in 2011. Additionally, a complete posterior mandibular unit of a large mosasaur from the type Maastrichtian of the Netherlands, collected some time prior to 1879 and previously identified as ‘Mosasaurus giganteus’, is described and reassigned here toPrognathodon saturator; historical issues surrounding the taxonomic attribution of this specimen are clarified. The new material extends the known geographic distribution ofPrognathodon saturatorandCarinodens belgicus.

Synapsida, the clade including therapsids and thus also mammals, is one of the two major branches of amniotes. Organismal design, with modularity as a concept, offers insights into the evolution of therapsids, a group that experienced profound anatomical transformations throughout the past 270Ma, eventually leading to the evolution of the mammalian bauplan. However, the anatomy of some therapsid groups remains obscure. Gorgonopsian braincase anatomy remains poorly known, and aspects of their brain anatomy, cranial nerves and vasculature, osseous labyrinth persist unknown. By using propagation phase contrast synchrotron micro-computed tomography, we scanned GPIT/RE/7124, a specimen previously reported as Aloposaurus gracilis. We explored the anatomy of the braincase and rendered the anatomy of the various skull cavities. Notably, we found that there is a separate ossification between what was previously referred as the “parasphenoid” and the basioccipital. This element is reinterpreted as a posterior ossification of the basisphenoid, the basi-postsphenoid. Additionally the previously called “parasphenoid” is in fact the co-ossification of the dermal parasphenoid and the endochondral basi-presphenoid. The anatomy of the osseous labyrinth is rendered in detail, revealing a unique discoid morphology of the horizontal semicircular canal, rather than toroidal, probably due to architectural contraints of the ossification of the opisthotic and supraoccipital. In addition, the orientation of the horizontal semicircular canal suggests an anteriorly tilted alert head posture. The morphology of the brain endocast is in accordance with the more reptilian endocast shape of other non-mammaliaform neotherapsids.

Upper Cretaceous marine rocks of the Big Bend Region of trans-Pecos Texas preserve a number of marine-adapted mosasauroids. At least three unnamed taxa of basal mosasauroids are represented by remains from shaly limestones in the middle Turonian portion of the Boquillas Formation. These occur along with remains of larger derived mosasaurs referable to Russellosaurina and an undescribed tylosaurine. Derived mosasaurs from the middle to late Coniacian include the first report of Tylosaurus kansasensis outside of Kansas, T. nepaeolicus, Platecarpus planifrons, and Platecarpus aff. P. planifrons. Clidastes liodontus is found in the latest Coniacian or early Santonian part of the Pen Formation. An undescribed species of Ectenosaurus, Clidastes sp. and an indeterminate plioplatecarpine occurs in the middle Santonian to early Campanian interval of the Pen Formation. The mosasaur fauna from the Big Bend region is quite similar to that from the Smoky Hill Chalk of Kansas, a thousand kilometres to the north. We refine the position of the Cenomanian–Turonian boundary within the Ernst Member of the Boquillas Formation, based on ammonite faunas. We also corroborate previous interpretations describing the time-transgressive nature of the onset of deposition of the Pen Formation based on a west-to-east descending level of the Inoceramus (Cremnoceramus) undulatoplicatus FAD.

New sauropod dinosaur material is described from Jones Ranch, Early Cretaceous of Texas (USA). Originally described as Paluxysaurus jonesi, the material from Jones Ranch has recently been referred to Sauroposeidon proteles. Elements newly prepared from dense concretionary matrix include the sacrum, ilium and proximal portion of the tail. Reconstructions of the skull and sacrum plus pelvic girdles are presented. ‘Paluxysaurus jonesi’ (=S. proteles) is a blunt-faced sauropod that was originally regarded as closely related to Brachiosaurus. Portions of the sacrum are now exposed and show that it is nearly complete, missing only parts of the first sacral (S1). The anterior sacrals are firmly fused, however, a newly discovered opisthocoelous last sacral (S6) remains unfused. A complete sequence of proximal caudal vertebrae shows a rapid transition from anteroposteriorly short and mediolaterally broad centra anteriorly, to more elongate cylindrical centra posteriorly. All proximal caudals have slightly amphicoelous centra. Some middle anterior caudals have a shallow longitudinal groove on the ventral surface of the centrum. Specimens from Jones Ranch exhibit characters of the sacrum and tail that clearly corroborate placement of ‘P. jonesi’ (Sauroposeidon proteles) as a somphospondylan titanosauriform.

Halisaurine mosasaurs are poorly known, represented by a small number of specimens from the Santonian-Maastrichtian (~86 Ma – ~66 Ma), but enjoyed broad palaeobiogeographic distribution during that time. They are important for understanding mosasaur evolution because certain aspects of their morphology retain the relatively plesiomorphic or minimally modified squamate conditions; however, existing material is limited and certain anatomical details are lacking. We report here two new specimens of Halisaurus arambourgi including a well-preserved, nearly complete skull and postcranial skeleton, and a partial skull that preserves details of the braincase and quadrate. We focus our description on morphology that augments the original description of this species and provides comparisons with other halisaurines. Braincase and temporal arcade characters confirm the plesiomorphic nature of Halisaurus, supporting a relatively basal position of Halisaurinae within Mosasauridae. Comparisons of cranial morphology support reconstruction of relationships within Halisaurinae, indicating that H. arambourgi is most closely related to H. platyspondylus, Phosphorosaurus (= H. ortliebi) is the sister taxon to those taxa, and Eonatator is the most basal described halisaurine. The proportions of the epipodials and the caudal vertebral centrum morphometrics indicate H. arambourgi is more derived than the Santonian to early Campanian Eonatator sternbergii but less derived than a Halisaurus sp. specimen from the mid-Maastrichtian of the Moreno Formation of California, USA. Moreover, vertebral morphometrics reveals that H. arambourgi possessed a downturned tail that likely supported a crescent-like fluke.

New material of Halisaurus platyspondylus allows description of the snout elements for the first time. The specimen was recovered from the Late Maastrichtian New Egypt Formation in Gloucester County, New Jersey. Portions of the frontal, both prefrontals, and the left quadrate are preserved and are nearly identical to the USNM H. platyspondylus specimen. It can be excluded from H. arambourgi by the extensive sutural contact of the prefrontal and ventral frontal. The new material demonstrates development of a relatively broad short skull in H. platyspondylus as in H. arambourgi, and articulations of constituent elements reveal a strong, akinetic snout. This stands in contrast to the elongate, narrow skulls of more basal halisaurines such as Eonatator. This pattern, also seen in derived members of other mosasaurid subfamilies, suggests a shift from high velocity jaw closure for prey acquisition in more basal forms to robust skulls optimized for increased bite force in some more derived forms.

Here we report the occurrence of Terminonaris represented by three specimens recovered from the early middle Cenomanian (96 Ma) Woodbine Formation of Lewisville Lake, Denton County, Texas. Crocodyl...

Incremental stages of major evolutionary transitions within a single animal lineage are rarely observed in the fossil record. However, the extraordinarily complete sequence of well preserved material spanning the 27-Myr existence of the marine squamate subfamily Mosasaurinae provides a unique exception. By comparison with extant and extinct analogs, the tail morphology of four mosasaurine genera is examined, revealing a pattern of evolution that begins with the generalized varanoid anatomy and culminates in a high-aspect-ratio fin, similar to that of sharks. However, unlike the epicercal caudal fluke of selachians in which the tail bends dorsocaudally, derived mosasaurs develop a hypocercal tail with a ventrocaudal bend. Progressive caudal regionalization, reduced intervertebral mobility, increased tail depth due to a marked downturn of the posterior caudal segment, and the development of finlike paired appendages reveal a pattern of adaptation toward an optimized marine existence. This change in morphology reflects a transition from anguilliform or sub-carangiform locomotion to carangiform locomotion, and indicates a progressive shift from nearshore dwellers to pelagic cruisers—a change in foraging habitat independently corroborated by paleobiogeographic, stable isotope, osteohistological, and paleopathological data. Evolutionary patterns similar to those observed in mosasaurine mosasaurs are seen in other secondarily aquatically adapted amniotes, notably metriorhynchid crocodyliforms, cetaceans, and ichthyosaurs, and may be explained by developmental modularity governing the observed phenotypic expression.

New mosasaur fossils from Maastrichtian beds at Bentiaba, Angola, representing elements of the skull and postcranial axial skeleton from two individuals of the durophagous genus Globidens, are reported. Based on dental morphology, specifically the inflated posterior surface and vertical sulci, the Bentiaba specimens are identified as Globidens phosphaticus, a species defined by characters of a composite dentition from the Maastrichtian of Morocco. Comparisons indicate that G. phosphaticus is most closely related to G. schurmanni, from the late Campanian of South Dakota, the youngest north American Globidens species at about 72.5 Ma. The morphology of the premaxilla and its relationship with the maxillae is unique among mosasaurs, and supports the taxonomic validity of G. phosphaticus. In contrast with earlier species of the genus, G. phosphaticus is currently known from north and west Africa, the Middle East and the central eastern margin of South America, suggesting it may have been restricted to the Maastrichtian tropical zone as previously hypothesised.

The Cretaceous tropical Atlantic Ocean was the setting for an initial tectonically controlled late Aptian shallow water (≤ 300 m) connection between the northern and southern portions of the Atlantic, followed by a deep-water connection by the Turonian. Ocean currents changed with deepening of the South Atlantic and progressive widening of the Equatorial Atlantic Gateway. Aptian evaporite deposition came to a halt. The Albian-Turonian interval includes a trend toward increasing sea level and was characterized by globally warm sea surface temperatures. Productive areas of coastal upwelling led to the deposition of organic-rich sediments varying in position along the African coast with time, culminating in the Benguela Upwelling that commenced in the Miocene. The drift of Africa in the Late Cretaceous indicates that throughout most of this period, the coastal area around the fossil locality of Iembe, north of Luanda, Angola, lay in arid latitudes (15o S to 30o S), which are generally characterized by sparse vegetation. This presumption is consistent with the utter lack of macroscopic terrestrial plant debris washed into near shore sedimentary environments and indicates that organic rich marine shales have a minimal terrestrial carbon component. The connection of the North and South Atlantic oceans severed a direct terrestrial dispersal route between South America and Africa, but opened a north-south dispersal route for marine amniotes. This seaway was used by late Turonian mosasaurs and sea turtles as evidenced by Angolasaurus and a new turtle taxon close to Sandownia, both found at Iembe and derived from northern clades. The presence of a sauropod in late Turonian sediments, also from Iembe, suggests that this animal was tolerant of warm, arid conditions as the desert elephants of Namibia are today. Further, it suggests that the waning terrestrial dispersal route between South America and Africa was situated in a region where high temperature, low rainfall, and sparse vegetation would be expected to restrict the movement of more mesic and ecologically sensitive species.

Timing and magnitude of surface uplift are key to understanding the impact of crustal deformation and topographic growth on atmospheric circulation, environmental conditions, and surface processes. Uplift of the East African Plateau is linked to mantle processes, but paleoaltimetry data are too scarce to constrain plateau evolution and subsequent vertical motions associated with rifting. Here, we assess the paleotopographic implications of a beaked whale fossil (Ziphiidae) from the Turkana region of Kenya found 740 km inland from the present-day coastline of the Indian Ocean at an elevation of 620 m. The specimen is similar to 17 My old and represents the oldest derived beaked whale known, consistent with molecular estimates of the emergence of modern straptoothed whales (Mesoplodon). The whale traveled from the Indian Ocean inland along an eastward-directed drainage system controlled by the Cretaceous Anza Graben and was stranded slightly above sea level. Surface uplift from near sea level coincides with paleoclimatic change from a humid environment to highly variable and much drier conditions, which altered biotic communities and drove evolution in east Africa, including that of primates.

The north-central Texas Cretaceous section and its contained fossils, as compared to sections at ‘Ein Yabrud in the eastern Mediterranean region, demonstrate that dolichosaurs and primitive mosasaurs inhabited marine environments at least from the intertidal zone to Haasiasaurus with marine snakes at ‘Ein Yabrud, suggest similar temperature requirements to modern sea snakes and marine iguanas (Amblyrhynchus cristatus), specifically sea-surface temperatures between approximately 20° and 30° С The Cenomanian and Turonian stages are characterised by widespread shallow seas with relatively high sea-surface temperatures extending to at least 45° N and 65° S latitude. The distribution of dolichosaurs, mosasaurs and snakes during this interval contradicts palaeoclimate models that predict high (>30° C) equatorial sea-surface temperatures and a steep latitudinal temperature gradient in the Northern Hemisphere.

A new mosasaur, Russellosaurus coheni, is described from the Collignoniceras woollgari Zone (lower Middle Turonian) at Cedar Hill, Dallas County, Texas. At approximately 92 Ma, it is the oldest well-preserved mosasaur skull from North America. It possesses characters diagnostic of Plioplatecarpinae but retains numerous plesiomorphies as well. Phylogenetic analysis indicates a close relationship with Yaguarasaurus columbianus, and these two, together with Tethysaurus nopcsai, form a clade that occupies a position basal to the divergence of the subfamilies Tylosaurinae and Plioplatecarpinae. Russellosaurus coheni is proposed as the nominal taxon of a new mosasaur clade, parafamily taxon novum Russellosaurina, which includes Plioplatecarpinae, Tylosaurinae, their common ancestor and all descendants. Tethysaurus retains a plesiopedal limb and girdle morphology, and along with Russellosaurus and Yaguarasaurus, cranial plesiomorphies. Dallasaurus turneri, a temporally and geographically sympatric plesiopedal mosasaur, occupies a basal position within Mosasaurinae. This phyletic arrangement confirms that marine adaptations, such as development of paddle-like limbs, occurred independently in at least two lineages of mosasaurs, once within Mosasaurinae and once within Russellosaurina.

Sediments in north-central Texas, ranging in age from >117 to 85 Ma, represent a variety of terrestrial and marine depositional settings. Isotopic analyses of wood fragments found throughout the section allow correlation to the standard secular marine δ13C curve because of characteristic peaks at the Aptian-Albian and Cenomanian-Turonian boundaries. Consistency of the north-central Texas δ13C curve with the marine standard facilitates correlation among non-marine and marine environments on a global scale. Radiometrically dated ammonite zones recognised in Texas provide calibration for the Cenomanian and Turonian portions of the section. Cenomanian and Turonian sediments in north-central Texas preserve the oldest (96 Ma) and the youngest (Coniasaurus, a dolichosaur also known from the southern North Sea Basin during that interval. Haasiasaurus, the oldest known well-documented early mosasaur, is found at ‘Ein Yabrud, Israel (98 Ma), followed by other poorly dated Cenomanian taxa from the eastern Mediterranean region, and then by Dallasaurus turneri and Russellosaurus coheni in Texas (92 Ma) and Tethysaurus (90.5 Ma) in Morocco. Neither shifts in δ13C nor large-scale sea level change seem to have influenced dolichosaur or mosasaur evolution in substantial ways during the Cenomanian and Turonian stages.

A new genus and species of primitive-limbed mosasauroid, Dallasaurus turneri, from the Middle Turonian (∼92 Ma) of north-central Texas, is described on the basis of two incomplete skeletons. The new taxon retains plesiomorphic characters such as facultatively terrestrial limbs (plesiopedal) but also exhibits certain characters shared with derived mosasaurs of the subfamily Mosasaurinae. In phylogenetic analysis, the new taxon reconstructs as the basal member of that clade. Other plesiopedal taxa previously included in the family Aigialosauridae reconstruct in basal positions within three different, major clades that include members that achieved the derived (hydropedal) fin-like limb condition. In addition, Opetiosaurus and Aigialosaurus reconstruct as successive outgroup taxa to all other mosasauroids, thereby demonstrating the paraphyletic nature of the current concept of Aigialosauridae. Interpretation of our phylogenetic analysis suggests that three different lineages of mosasauroids independently achieved the derived mosasaur body plan, including fully marine limb modifications culminating in the development of flippers or paddle-like appendages. The inclusion of plesiopedal forms within lineages of well-established hydropedal clades requires a reorganisation of our concepts of Mosasauridae to include these basal forms. In order to avoid continued use of the paraphyletic taxon ‘Aigialosauridae’ as currently defined, we recommend ‘Aigialosauridae’ as a formal taxonomic name be used only for inclusion of Aigialosaurus dalmaticus and potential members of its own independent lineage. This also avoids the implicit polyphyletic use of ‘Mosasauridae’. Additionally, the diagnosis of Mosasauridae should be modified to exclude limb characters that discriminate between more terrestrial versus more aquatic adaptations.

We describe a new marine varanoid, Judeasaurus tchernovi gen. et sp. nov., on the basis of a partial skull recovered from the Middle Cenomanian of the Judean Hills. The new taxon possesses a unique suite of characters exhibited in terrestrial varanoid lizards on the one hand and derived mosasauroids on the other. The characters that relate it to terrestrial varanoid lizards include broad premaxilla, anteriorly depressed maxillae underlying the nasal capsule, extensive postorbitofrontal-parietal contact and vertically oriented parietal rami. Derived mosasauroid characters include a question-mark shaped quadrate, fused frontals, intricate fronto-parietal suture and moderately retracted nares. The shape of the supratemporal and its syndesmotic articulation with the parietal distinguishes the new taxon from any other known specimen. The dentition exhibits elongate and narrow cylindrical roots lacking resorption pits, a condition reminiscent of Coniasaurus, but crowns are small, slightly recurved and conical. Taken together, the new taxon possesses a suite of characters suggesting dolichosaurid affinities.

The fossil snake speciesHaasiophis terrasanctusTchernov, Rieppel, Zaher, Polcyn, and Jacobs, 2000, from the early Upper Cretaceous of the Middle East, is described and illustrated, following a review of the current debate on snake relationships and origins. The description and discussion presented here adds important detail to the knowledge of this taxon and its phylogenetic significance beyond the limited account presented in the original description ofHaasiophis. The species is remarkable in that it shows the skull of a relatively advanced (i.e., macrostomatan) snake, yet preserves well-developed hind limbs. The hind limb includes a femur, tibia, fibula, astragalus, calcaneum, distal tarsal four, and remains of four metatarsals and two phalanges.Haasiophiscannot be considered a juvenile specimen ofPachyrhachis. The implications of the presence of well-developed hind limbs inHaasiophis, Pachyrhachis, andPodophisfor the cladistic analysis of the phylogenetic interrelationships of these fossil snakes is discussed. The presence of well-developed hind limbs inPachyrhachisandHaasiophisalso creates methodological problems for the cladistic analysis of the phylogenetic relationships of these fossil snakes. Scenarios of snake origins are reviewed and found to be deficient in the absence of a well-corroborated hypothesis of snake relationships within Squamata.

The fossil snake species Haasiophis terrasanctus Tchernov, Rieppel, Zaher, Polcyn, and Jacobs, 2000, from the early Upper Cretaceous of the Middle East, is described and illustrated, following a review of the current debate on snake relationships and origins. The description and discussion presented here adds important detail to the knowledge of this taxon and its phylogenetic significance beyond the limited account presented in the original description of Haasiophis. The species is remarkable in that it shows the skull of a relatively advanced (i.e., macrostomatan) snake, yet preserves well-developed hind limbs. The hind limb includes a femur, tibia, fibula, astragalus, calcaneum, distal tarsal four, and remains of four metatarsals and two phalanges. Haasiophis cannot be considered a juvenile specimen of Pachyrhachis. The implications of the presence of well-developed hind limbs in Haasiophis, Pachyrhachis, and Podophis for the cladistic analysis of the phylogenetic interrelationships of these f...

We report here a new elasmosaurid from the early Maastrichtian at Bentiaba, southern Angola. Phylogenetic analysis places the new taxon as the sister taxon toStyxosaurus snowii, and that clade as the sister of a clade composed of (Hydrotherosaurus alexandrae(Libonectes morgani+Elasmosaurus platyurus)). The new taxon has a reduced dorsal blade of the scapula, a feature unique amongst elasmosaurids, but convergent with cryptoclidid plesiosaurs, and indicates a longitudinal protraction-retraction limb cycle rowing style with simple pitch rotation at the glenohumeral articulation. Morphometric phylogenetic analysis of the coracoids of 40 eosauropterygian taxa suggests that there was a broad range of swimming styles within the clade.

Throughout the animal kingdom, adaptive colouration serves critical functions ranging from inconspicuous camouflage to ostentatious sexual display, and can provide important information about the environment and biology of a particular organism. The most ubiquitous and abundant pigment, melanin, also has a diverse range of non-visual roles, including thermoregulation in ectotherms. However, little is known about the functional evolution of this important biochrome through deep time, owing to our limited ability to unambiguously identify traces of it in the fossil record. Here we present direct chemical evidence of pigmentation in fossilized skin, from three distantly related marine reptiles: a leatherback turtle, a mosasaur and an ichthyosaur. We demonstrate that dark traces of soft tissue in these fossils are dominated by molecularly preserved eumelanin, in intimate association with fossilized melanosomes. In addition, we suggest that contrary to the countershading of many pelagic animals, at least some ichthyosaurs were uniformly dark-coloured in life. Our analyses expand current knowledge of pigmentation in fossil integument beyond that of feathers, allowing for the reconstruction of colour over much greater ranges of extinct taxa and anatomy. In turn, our results provide evidence of convergent melanism in three disparate lineages of secondarily aquatic tetrapods. Based on extant marine analogues, we propose that the benefits of thermoregulation and/or crypsis are likely to have contributed to this melanisation, with the former having implications for the ability of each group to exploit cold environments.

Mosasaurs are secondarily aquatic squamates that became the dominant marine reptiles in the Late Cretaceous about 98-66 million years ago. Although early members of the group possessed body shapes similar to extant monitor lizards, derived forms have traditionally been portrayed as long, sleek animals with broadened, yet ultimately tapering tails. Here we report an extraordinary mosasaur fossil from the Maastrichtian of Harrana in central Jordan, which preserves soft tissues, including high fidelity outlines of a caudal fluke and flippers. This specimen provides the first indisputable evidence that derived mosasaurs were propelled by hypocercal tail fins, a hypothesis that was previously based on comparative skeletal anatomy alone. Ecomorphological comparisons suggest that derived mosasaurs were similar to pelagic sharks in terms of swimming performance, a finding that significantly expands our understanding of the level of aquatic adaptation achieved by these seagoing lizards.

International audience; Background: During their evolution in the Late Cretaceous, mosasauroids attained a worldwide distribution, accompanied by a marked increase in body size and open ocean adaptations. This transition from land-dwellers to highly marine-adapted forms is readily apparent not only at the gross anatomic level but also in their inner bone architecture, which underwent profound modifications.Methodology/Principal Findings: The present contribution describes, both qualitatively and quantitatively, the internal organization (microanatomy) and tissue types and characteristics (histology) of propodial and epipodial bones in one lineage of mosasauroids; i.e., the subfamily Mosasaurinae. By using microanatomical and histological data from limb bones in combination with recently acquired knowledge on the inner structure of ribs and vertebrae, and through comparisons with extant squamates and semi-aquatic to fully marine amniotes, we infer possible implications on mosasaurine evolution, aquatic adaptation, growth rates, and basal metabolic rates. Notably, we observe the occurrence of an unusual type of parallel-fibered bone, with large and randomly shaped osteocyte lacunae (otherwise typical of fibrous bone) and particular microanatomical features in Dallasaurus, which displays, rather than a spongious inner organization, bone mass increase in its humeri and a tubular organization in its femora and ribs.Conclusions/Significance: The dominance of an unusual type of parallel-fibered bone suggests growth rates and, by extension, basal metabolic rates intermediate between that of the extant leatherback turtle, Dermochelys, and those suggested for plesiosaur and ichthyosaur reptiles. Moreover, the microanatomical features of the relatively primitive genus Dallasaurus differ from those of more derived mosasaurines, indicating an intermediate stage of adaptation for a marine existence. The more complete image of the various microanatomical trends observed in mosasaurine skeletal elements supports the evolutionary convergence between this lineage of secondarily aquatically adapted squamates and cetaceans in the ecological transition from a coastal to a pelagic lifestyle.

A forelimb of a new sauropod dinosaur (Angolatitan adamastor n. gen. et sp.) from the Late Turonian of Iembe (Bengo Province) represents the first dinosaur discovery in Angola, and is one of the few occurrences of sauropod dinosaurs in sub-Saharan Africa collected with good chronological controls. The marginal marine sediments yielding the specimen are reported to be late Turonian in age and, thus it represents a non-titanosaurian sauropod in sub-Saharan Africa at a time taken to be dominated by titanosaurian forms. Moreover, Angolatitan adamastor is the only basal Somphospondyli known in the Late Cretaceous which implies in the existence of relict forms in Africa.Um membro anterior de um novo dinossauro saurópode (Angolatitan adamastor n. gen. et sp.) do Turoniano Superior de Iembe (Bengo) representa a descoberta do primeiro dinossauro em Angola e é uma das poucas ocorrências de dinossauros saurópodes na África Subsaariana recolhidos com bons controles cronológicos. Os sedimentos marinhos marginais de onde provém o espécime estão datados do Turoniano superior e, portanto, trata-se de um saurópodes não-titanossauro na África subsaariana onde predominavam titanossauros. Além disso, Angolatitan adamastor é o único Somphospondyli basal conhecido no Cretáceo Superior, o que implica a sobrevivência de formas-relíquia na África.

Low concentrations of the structural protein collagen have recently been reported in dinosaur fossils based primarily on mass spectrometric analyses of whole bone extracts. However, direct spectroscopic characterization of isolated fibrous bone tissues, a crucial test of hypotheses of biomolecular preservation over deep time, has not been performed. Here, we demonstrate that endogenous proteinaceous molecules are retained in a humerus from a Late Cretaceous mosasaur (an extinct giant marine lizard). In situ immunofluorescence of demineralized bone extracts shows reactivity to antibodies raised against type I collagen, and amino acid analyses of soluble proteins extracted from the bone exhibit a composition indicative of structural proteins or their breakdown products. These data are corroborated by synchrotron radiation-based infrared microspectroscopic studies demonstrating that amino acid containing matter is located in bone matrix fibrils that express imprints of the characteristic 67 nm D-periodicity typical of collagen. Moreover, the fibrils differ significantly in spectral signature from those of potential modern bacterial contaminants, such as biofilms and collagen-like proteins. Thus, the preservation of primary soft tissues and biomolecules is not limited to large-sized bones buried in fluvial sandstone environments, but also occurs in relatively small-sized skeletal elements deposited in marine sediments.

A 95-million-year-old fossil snake from the Middle East documents the most extreme hindlimb development of any known member of that group, as it preserves the tibia, fibula, tarsals, metatarsals, and phalanges. It is more complete than Pachyrhachis , a second fossil snake with hindlimbs that was recently portrayed to be basal to all other snakes. Phylogenetic analysis of the relationships of the new taxon, as well as reanalysis of Pachyrhachis , shows both to be related to macrostomatans, a group that includes relatively advanced snakes such as pythons, boas, and colubroids to the exclusion of more primitive snakes such as blindsnakes and pipesnakes.

A new Late Cretaceous turtle, Angolachelys mbaxi gen. et sp. nov., from the Turonian (90 Mya) of Angola, represents the oldest eucryptodire from Africa. Phylogenetic analysis recovers Angolachelys mbaxi as the sister taxon of Sandownia harrisi from the Aptian of Isle of Wight, England. An unnamed turtle from the Albian Glen Rose Formation of Texas (USA) and the Kimmeridgian turtle Solnhofia parsonsi (Germany), are successively more distant sister taxa. Bootstrap analysis suggests those four taxa together form a previously unrecognized monophyletic clade of marine turtles, herein named Angolachelonia clade nov., supported by the following synapomorphies: mandibular articulation of quadrate aligned with or posterior to the occiput, and basisphenoid not visible or visibility greatly reduced in ventral view. Basal eucryptodires and angolachelonians originated in the northern hemisphere, thus Angolachelys represents one of the first marine amniote lineages to have invaded the South Atlantic after separation of Africa and South America.