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SummaryHow infection by a viral variant showing antigenic drift impacts a preformed mature human memory B cell (MBC) repertoire remains an open question. Here, we studied the MBC response up to 6 months after Omicron BA.1 breakthrough infection in individuals previously vaccinated with three doses of mRNA vaccine. Longitudinal analysis, using single-cell multi-omics and functional analysis of monoclonal antibodies from RBD-specific MBCs, revealed that a BA.1 breakthrough infection mostly recruited pre-existing cross-reactive MBCs with limitedde novoresponse against BA.1-restricted epitopes. Reorganization of clonal hierarchy and new rounds of germinal center reaction, however, combined to maintain diversity and induce progressive maturation of the MBC repertoire against common Hu-1 and BA.1, but not BA.5-restricted, SARS-CoV-2 Spike RBD epitopes. Such remodeling was further associated with marked improvement in overall neutralizing breadth and potency. These findings have fundamental implications for the design of future vaccination booster strategies.

Morphotype A (Fig. 4 A-E) Dorsal view The sagittal groove is rather marked. The proximal part of the tuber calcanei is rather mediolaterally wide. It is rather proximodistally elongated, as is the ectal facet. This facet is highly convex. Its edges are rather well pronounced, except the distal one, which merges with the body of the calcaneus (and therefore is difficult to delimit). The sustentacular facet is well-rounded, very slightly concave, and extends on the proximal edge of the sustentaculum tali. The peroneal process is quite broad and its proximal edge is well-defined. The cuboid facet is inclined with respect to the mediolateral axis and its lateral edge rises slightly on the body of the calcaneus. This articular surface is strongly concave. Lateral view The dorsal and ventral edges of the tuber calcanei are slightly concave. A cavity – probably for the insertion of the lateral collateral ligament – is clearly visible proximal to the ectal facet. Medial view The tendinous plantar groove is well excavated. The sustentaculum tali is dorsoventrally quite thick, even more so than in Cynodictis lacustris and Morphotype B. The plantar tubercle does not form a distally directed tip as seen in Cynodictis lacustris. Distal view The plantar tubercle is ventrally broad. The edge separating the plantar tubercule and the cuboid facet is more visible than in Cynodictis lacustris. Proximal view The proximal part of the tuber calcanei has a sub-spherical surface. The groove is slightly more pronounced than in Cynodictis lacustris.

Morphotype 3 (Fig. 3 K-O) Dorsal view The trochlea is weakly excavated. The medial and lateral lips are of different proximodistal length, the lateral being shorter than the medial. The proximal plantar tuberosity is very slightly broad. The neck is short. In two specimens (MNHN.F.Qu10042 and MNHN.F.Qu10367), the neck is slightly longer than in the others, but these two specimens do not differ enough to represent another morphotype. The head is broad and projected on the medial side. It has more pronounced edges on the lateral side than on the medial one and rises strongly on the medial edge of the neck, reaching the level of the most distal edge of the trochlea. Ventral View The medial and lateral edges of the ectal facet are curved (more on the medial than on the lateral edge). A foramen is visible at the proximal level. The sustentacular facet has a rhomboidal area. Its edges are marked. The facet is slightly convex except on its proximomedial extension, where it becomes concave. In two specimens (MNHN.F.Qu10042 and MNHN.F.Qu10367), the sustentacular facet is slightly less elongated and more proximally positioned on the body than in the others. Lateral view The edges of the fibular facet are relatively rounded, giving this facet a half-moon look, as in Morphotype 2. The ectal facet is sharply convex. Distal view The axis of elongation of the head is slightly inclined with respect to the mediolateral axis of the astragalus. The lateral process is only slightly broad. Proximal view The trochlear foramen is absent in some specimens and present in others. The proximoventral edge of the medial lip of the trochlea (trochlea tali proximalis) forms a small ventral point. The tendinous plantar groove is present but weakly excavated and is well inclined relative to the axis of the trochlea.

Morphotype 4 (Fig. 3 P-T) Dorsal view The trochlea is shallow. The medial and lateral lips are more or less parallel to each other, but of different proximodistal lengths, and have a distal edge of the medial lip that is more proximal than the lateral lip. The proximal plantar tuberosity is a little broader than in Morphotype 3. The neck is longer than in Morphotype 3. The head is quite large and a little projected on the medial side. It has more pronounced edges than in Morphotype 3 and extends much less on the neck of the medial side of the astragalus. The medial edge of the head is well separated from the distal edge of the medial lip of the trochlea. Ventral view The medial and lateral edges of the ectal facet have a strong curvature. The sustentacular facet has a rhomboidal area. Its edges are well pronounced. This facet is slightly convex except on its proximomedial extension, where it becomes concave. Lateral view The proximomedial edge of the fibular facet is less rounded than in Morphotype 3 and therefore displays a somewhat rectangular shape. The ectal facet is sharply convex. ll ml A B ppt tr sf n sit C D ef lp ff E h ptg F G H I J K L P Q f M N O R S T Distal view The axis of elongation of the head is along the mediolateral axis of the astragalus. The lateral process is very little broad. Proximal view The trochlear foramen is absent. The proximoventral edge of the medial lip of the trochlea forms a ventral tip. The plantar tendon groove is well marked, very inclined relative to the axis of the trochlea, and well excavated. CALCANEUS DESCRIPTIONS For all morphotypes, the medial process of the tuber calcanei is proximally longer than the lateral process. A groove on the proximal surface of the tuber calcanei, positioned rather ventrally, is clearly visible. The cuboid facet is larger mediolaterally than proximodistally. Three different morphotypes have been determined based on differences in size and morphology.

Morphotype 2 (Fig. 3 F-J) Dorsal view The trochlea is deeply excavated. The medial and lateral edges are relatively equal. The trochlea extends a little distally on the neck, almost forming a squatting facet. The proximal plantar tuberosity is weakly broad. The neck is thin and more mediolaterally extended than the head. The neck is longer than that of Morphotype 1. The head is a little projected on the medial side (much less than in Morphotype 1) and its edges are not pronounced. It rises strongly on the medial edge of the neck, up to the level of the distal edge of the medial lip. Ventral View The ectal facet has little curvature on its medial and lateral margins. The foramen at the proximal level of this sinus is visible. The sustentacular facet is proximodistally elongated. Its lateral edge is rather marked, contrary to the other edges. The facet is slightly convex except on its proximomedial extension, where it becomes concave. Lateral view The edges of the fibular facet are relatively rounded, giving this facet a half-moon shape. The ectal facet is sharply convex. Distal view The axis of elongation of the head is inclined relative to the mediolateral axis of the astragalus. The lateral process is weak or absent. Proximal view The trochlear foramen is wide. The tendinous plantar groove is weakly excavated and is inclined almost 90° with respect to the axis of the trochlea.

Morphotype B (Fig. 4 F-J) Dorsal view The sagittal groove is rather visible. The tuber calcanei is proximodistally quite elongated. The ectal facet is more inclined relative to the proximodistal axis than in other morphotypes, as well as in Cynodictis lacustris. It is strongly convex in the middle and very slightly concave in its proximal part. The edges of this facet are rather well pronounced, except the distal edge, which merges with the body of the calcaneus and is therefore difficult to delimit. The sustentacular facet is rounded and extends slightly on the proximal edge of the sustentaculum tali. It is placed more proximal on the body of the calcaneus than in the other two calcaneal morphotypes. The peroneal process and its proximal and distal edges are quite well defined. The cuboid facet is inclined with respect to the mediolateral axis and its lateral edge rises over the body of the calcaneus. The plantar tubercle is distally very long and clearly visible in dorsal view. It is longer than that of Cynodictis lacustris. Lateral view The dorsal and ventral edges of the tuber calcanei are very slightly concave. The cavity, proximal to the ectal facet, is deep and positioned higher on the tuber than in Morphotype A. Medial view The tendinous plantar groove is quite excavated. Distal view The cuboid facet is smaller than in Morphotype A. The plantar tubercle is ventrally quite broad. The edge separating these two structures is not very clear. Proximal view The proximal part of the tuber calcanei has a rather oval surface that is slightly dorsoventrally elongated.

Morphotype 1 (Fig. 3 A-E) Dorsal view The trochlea is somewhat shallow. Its medial and lateral edges are more or less parallel to each other and are of different proximodistal lengths, the lateral edge being much shorter than the medial one. The proximal plantar tuberosity is present and slightly broad. The neck is thin, short and more mediolaterally extended than the head. The head is broad and projected on the medial side. It has strongly pronounced edges, rising on the neck at the medial side of the astragalus and reaching the level of the most distal edge of the trochlea. Ventral view The medial and lateral edges of the ectal facet have fairly strong curvatures. The foramen at the proximal level of this sinus is visible on some specimens.The sustentacular facet is quite large and occupies a large part of the neck width. It looks almost rhomboidal and its edges are strongly marked. The facet is slightly convex except on its proximomedial extension, where it becomes concave. Lateral view The proximomedial edge of the fibular facet forms a nearly right angle with the distal edge.The distal edge is flat, giving the facet a rectangular appearance. The ectal facet is shallow. Distal view The head has a groove in the center. The axis of elongation of the head is in the mediolateral axis of the astragalus. The lateral process is poorly broad. Proximal view The proximoventral part of the medial edge of the trochlea forms a ventral tip. The trochlear foramen is absent. The tendinous plantar groove is strongly excavated, rather mediolaterally thin, inclined with respect to the axis of the trochlea, and very deep., Published as part of Fournier, Morgane, Ladevèze, Sandrine, Verger, Kévin Le, Fischer, Valentin, Speijer, Robert P. & Solé, Floréal, 2020, On the morphology of the astragalus and calcaneus of the amphicyonids (Carnivora, Mammalia) from the Paleogene of Europe: implications for the ecology of the European bear-dogs, pp. 305-325 in Geodiversitas 42 (18) on page 313, DOI: 10.5252/geodiversitas2020v42a18, http://zenodo.org/record/3952805

Morphotype C (Fig. 4 K-O) Dorsal view The sagittal groove is poorly defined. The tuber calcanei is proximodistally quite elongated. The ectal facet is convex in the middle and very slightly concave in its proximal part. The edges of this facet are rather clear, except the distal edge, which merges with the body of the calcaneus (and is therefore difficult to delimit). The sustentaculum tali has a rounded articular surface, as in Morphotypes A and B, and extends slightly on the proximal edge. The peroneal process is not broad and merged with the ridge extending up on the tuber calcanei. The cuboid facet is concave and inclined with respect to the mediolateral axis, but its lateral edge does not extend up the body of the calcaneus as seen in Morphotypes A and B. Lateral view The dorsal and plantar edges of the tuber calcanei are very slightly concave. The cavity, which is proximal to the ectal facet, is not very deep. Medial view The tendinous plantar groove is not very marked. The sustentaculum tali is dorsoventrally quite thick, as in Morphotype A. Distal view The plantar tubercle is ventrally well broad. Proximal View The edges of the proximal part of the tuber calcanei are quite irregular. COMPARISON These morphotypes exhibit morphological differences from tarsal bones of Hyaenodonta, such as G. chronius (Zack & Rose 2015) and Hyaenodon (Bastl 2012). The neck of the astragalus is mediolaterally thinner and the medial edge of the head is more pronounced in these morphotypes. The plantar tendon groove is less pronounced, the proximal plantar tuberosity and the lateral processes are slenderer. The calcaneus of the morphotypes has a much less inclined cuboid facet than in I. raoi (Rana et al. 2015) and G. chronius (Zack & Rose 2015). In comparison with Nimravidae, such as H. primaevus and N. brachyops (Barrett 2016), all astragalus morphotypes have a longer neck and the head extends less on the medial side of this neck. The calcanei have a thinner sustentaculum tali and a shallower plantar tendon groove than in Nimravidae. Compared to Miacidae such as Vulpavus (Heinrich & Rose 1997), the tarsal bones of the morphotypes are smaller, and the four astragalar morphotypes have a shorter neck, which is less medially projected, and a less pronounced plantar tendon groove, which is less dorsally extended. Moreover, the sustentaculum tali is medially thinner and not as distally positioned as in Vulpavus. These morphotypes are also very different from those of Ursoidea such as Ursus spelaeus (Santi et al. 2005) and Ursus arctos (Baryshnikov 2015). They have less robust tarsal bones, the neck of the astragalus is much longer and the trochlea is mediolaterally thinner. The tuber calcanei is mediolaterally narrower, the sustentaculum tali is less distally positioned and its sustentacular facet is more rounded, not as elongated, and not inclined in the medioproximal-laterodistal direction as observed in ursoids. Compared to the ailurid Simocyon batalleri (Salesa et al. 2008), the morphotypes have a less flattened astragalar head, and a mediolaterally broader sustentacular facet. The sustentaculum tali is proximodistally thinner, the peroneal process is mediolaterally and proximodistally thinner and the plantar tendon groove is less marked than in S. batalleri. Compared to mustelids such as M. sansaniensis, I. zibethoides and T. sansaniensis (Peign�� 2012), the astragalar neck of the morphotypes is shorter and less medially projected, and he sustentacular facet is mediolaterally broader. The calcaneus morphotypes are larger with a more rounded sustentaculum tali. All these differences exclude an assignment of the bones to Hyaenodonta, Nimravidae, Miacidae, Ursidae, Ailuridae or Mustelidae and indicate a close relationship to amphicyonids. The astragalus of Morphotypes 1, 3, and 4 is very similar to that generally observed in Amphicyonidae such as Amphicyon major (Argot 2010), Amphicyon galushai (Hunt 2009), and the North American Ysengrinia americana Wortman, 1901 (Oligo- Miocene) (Hunt 2002). The head is relatively projected on the medial side of the astragalus and quite broad; the trochlea is asymmetrical and its mediolateral width is greater than its proximodistal length. Futhermore, Morphotype 1 displays a relatively large trochlea, just as Morphotype 2, which also features a deep trochlear articulation. These characteristics are present in large amphicyonids such as Amphicyon giganteus (Miocene of Europe and Africa; Gagnaison et al. 2017). Despite these morphological similarities, these three morphotypes display some differences from these amphicyonids (i.e., A. major, A. galushai, and Y. americana). The neck of Morphotype 1 is mediolaterally thinner and proximodistally shorter, and the fibular facet is dorsoventrally thicker than in Morphotypes 3 and 4. Moreover, Morphotype 1 is taller than the two others. The neck of Morphotype 3 is proximodistally longer and the head edges are less marked than in the others. In Morphotype 4, the distal edge of the trochlea medial lip is more proximal than the lateral lip and the plantar tendon groove is more marked. Morphotype 2 is assigned to Amphicyonidae because of its strong resemblance to the amphicyonid Daphoenodon robustum (North America, Miocene) (Hunt 2009). Indeed, the shape of the trochlea, relatively well excavated, the elongated neck, and the shape of the head, which is not mediolaterally wide in comparison to the width of the neck, are observed in Daphoenodon robustum. The morphology of the calcaneus Morphotype A is closely similar to that of Amphicyon galushai (Hunt 2009), which also has a broad tubercle on its proximal part that is much thinner on its distal part. Moreover, the sustentacular facet is rounded and distally placed. Morphotype B is similar to the specimen of Daphoenodon robustum illustrated in Hunt (2009). The sustentaculum tali is more proximally located than in the other morphotypes. The plantar tubercle is ventrally and distally long, forming a tip at the cuboid facet. Morphotype C is morphologically similar to the calcaneus of the European Amphicyon lathanicus Ginsburg, Cheneval, Janvier, Pouit & Sen, 2000 (Miocene) (Ginsburg 2002). The sustentaculum tali is distally located, the cuboid facet is inclined with respect to the mediolateral axis and is distally strongly concave. Its morphology is also strongly similar to that of Cynelos lemanensis Pomel, 1846 (Peign�� & Heizmann 2003), Afrocyon ginsburgi Morales, Pickford, Soria & Fraile, 1998 (Morales et al. 2016) and Amphicyon longiramus White, 1942 (Olsen 1960). The four amphicyonids share the following features: the peroneal process is poorly broad, the sustentaculum tali is distally positioned and the cuboid facet is concave. Moreover, the sustentacular facet is rounded in both C. lemanensis and Morphotype C. At the opposite side, the sagittal groove is more defined and the tuber calcanei is distally a little thinner in C. lemanensis. Relative abundance and body mass (see below) support the attribution of these morphotypes to amphicyonids, but they cannot be further assigned to infra-familial ranks. RELATIVE ABUNDANCES In almost all collections studied here, amphicyonids are by far the most abundant group (Table 2). This is also true for the dental specimens of this carnivoran group in the ULiege collection, with 30.73%. Amphicyonids are not the most abundant carnivorans in the KUL collection, but still represent 31.03% of the assemblage, making it the second most abundant group in this collection after Ursoidea (39.66%). The high relative abundance of amphicyonid tarsal bones is thus congruent with the high relative abundance of amphicyonids based on dental remains. BODY MASS ESTIMATION The body mass estimated for Cynodictis lacustris based on its astragalus (1 to 2 kg; Table 4) is lower than the values obtained from dental material (c. 5 kg; Table 3). For the European amphicyonids, the body mass estimated from the lower first molar varies between 4 and 134 kg (Table 3). This range is very broad and is greater than the values obtained for the four astragalar morphotypes. Morphotypes 1 and 2 fall within this range, but Morphotypes 3 and 4 are just outside this range with values below 3 kg; one can note that the latter case is similar to that of C. lacustris (Table 4). Among the amphicyonids recorded in the Paleogene of Europe (Table 3), body masses between 5 and 10 kg correspond to the genera Cynodictis, Symplectocyon Springhorn, 1979, and ��� Cynodictis ��� (C. exilis Teilhard de Chardin, 1915 and ��� C. ��� palmidens Teilhard de Chardin, 1915). Therefore, Morphotypes 3 and 4 might correspond to these genera. Morphotype 1 groups heavier specimens (between 8 and 17 kg based on astragalus; Table 4). Because it seems that the body masses estimated from the astragalus are lower than those estimated from the m1, Morphotype 1 could correspond to the smallest species of Cynelos, Cynelos rugosidens Schlosser, 1899 or Cynelos crassidens Filhol, 1876 (��� 23-24 kg). Some specimens could also correspond to the Oligocene amphicyonid Goupilictis Ginsburg, 1969 (13 kg). Finally, Morphotype 2 could also include specimens that correspond to the genus Cynelos Jourdan, 1862. It may also include representatives of the genera Pseudocyonopsis Kuss, 1965 and Haplocyon Schlosser, 1901 (Table 3). Interestingly these new tarsal bones indicate significant differences in body mass within the same family (Table 4), as does the dental material (Table 3). Furthermore, there are no specimens that may correspond to the largest European amphicyonids Brachycyon Filhol, 1872, Harpagocyon Springhorn, 1977, Ysengrinia Ginsburg, 1965, Haplocyonopsis Bonis, 1973, and Crassidia Heizmann & Kordikova, 2000. It is worth noting that these genera are only known in the Chattian (MP26-MP30). Thus, the astragali studied here might come from Priabonian and Rupelian localities, except if some belong to Goupilictis. LOCOMOTION Posture and locomotion significantly affect the morphology of the tarsal bones (Szalay & Decker 1974; Jenkins & McClearn 1984; Taylor 1989). The crurotarsal joint, where the tibia and astragalus are in contact, is the main axis of flexion of the foot. The posture is therefore related to the morphology of this articulation (Wang 1993). The calcaneus, which articulates with the astragalus, also has an important role in the movement of the hindlimb because of the insertion of the m. gastrocnemius and m. soleus. They attach to its distal end via the achilles tendon, which constitutes the main lever of plantar flexion (Barone 2000). Among the Carnivora, two postures are recognized: plantigrady and digitigrady. Some authors define an intermediate state present in many extant Mustelidae and Viverridae: semi-digitigrady (Wang 1993; Polly 2008). It appears that the absence of the trochlear foramen and a tendinous groove in digitigrade predators allows the tibia to rotate over the entire surface of the trochlea and thus to have a greater amplitude of flexion-extension (Wang 1993). According to Ginsburg (1961), an elongated astragalus is associated with digitigrade locomotion. Carrano (1997) remarked that the orientation of the astragalus head is a distinctive element between digitigrade and plantigrade postures: the head is oriented in the same direction as the body in dorsal view in a plantigrade mammal, whereas in a digitigrade mammal, it is inclined relative to the direction of the body of the astragalus. According to Polly (2008), in a digitigrade animal the calcaneal ectal facet is sharply convex, the peroneal process is small, the sustentaculum tali is more proximally and posteriorly positioned, and the astragalar ectal facet is sharply curved. In plantigrade animals: the calcaneal ectal facet is rounded, the peroneal process is long, the sutentaculum tali is larger and distally positioned, the astragalar neck is narrow, and the astragalar ectal facet is shallow. Finally, the presence of large and flat facets on these two bones causes a reduction of intertarsal mobility (Polly 2008). All the postures and locomotion hypothesized for the sample presented herein are listed in Table 6. Morphotype 1 has a plantar tendinous groove, and the head is not inclined towards the mediolateral axis. The ectal facet is shallow, as for Ailurus fulgens Cuvier, 1825 (Ailuridae) and Bassaricyon gabbii Allen, 1876 (Procyonidae), two plantigrade species (Polly 2008). It has a narrow neck and an ectal facet that is shallow. These characters suggest that Morphotype 1 corresponds to a plantigrade animal. Morphotype 2 has a longer neck than in Morphotype 1, and a head that is slightly inclined towards the mediolateral axis. The neck is also larger and the ectal facet is sharply curved, as observed in Canis lupus Linnaeus, 1758 (Canidae), Felis catus Linnaeus, 1758, Leptailurus serval (Schreber, 1776), and Lynx rufus (Schreber, 1777) (Felidae), which are all digitigrade (Polly 2008). Morphotype 2 therefore better corresponds to a digitigrade animal. Moreover, it strongly resembles the astragalus of the North American amphicyonid Daphoenodon robustum, which was considered a digitigrade animal capable of powerful propulsive force (Hunt 2009). However, Morphotype 2 has a tendinous groove, which is placed fairly ventrally on the trochlea and weakly excavated. Flexion-extension should therefore have moderate amplitude, but more than a plantigrade animal with a strongly defined tendinous groove. Daphoenodon robustum does not appear to have a tendinous groove (Hunt 2009 does not mention this structure, which is also not visible on the illustrations). Because of this morphology, Morphotype 2 is probably better characterized as a semi-digitigrade animal. Morphotypes 3 and 4 have a head that is oriented on the mediolateral axis as well as a plantar tendon groove, like in the plantigrade species used in Carrano���s (1997) analyses and Procyon lotor Linnaeus, 1758 (Procyonidae) (Wang 1993). The neck is long and narrow and the ectal facet is well curved (deeper in Morphotype 3 than in Morphotype 4), as in B. gabbii and A. fulgens, which are plantigrade mammals (Polly 2008). Morphotypes 3 and 4 are therefore interpreted as plantigrade, but the latter displays a larger range of movements enabled by a less deep trochlear surface. Morphotypes A and C have a rounded sutentaculum tali that is rather distal; this structure is even more distal in Morphotype C, as observed in A. fulgens and B. gabbii, which are plantigrade (Polly 2008). This would therefore be characteristic of a plantigrade animal. However, in Morphotype C, the peroneal process is poorly broad, which seems to be a digitigrade feature (e.g., L. serval; Polly 2008). The gear ratio for morphotype A is 1.23 (Table 5), which is similar to that of Vulpes velox (Say, 1823) (Canidae; digitigrade, terrestrial), Spilogale gracilis (Linnaeus, 1758) (Mephitidae; plantigrade, terrestrial), Taxidea taxus (Schreber, 1777) (Mustelidae; plantigrade, semifossorial), and Nasua narica (Linnaeus, 1766) (Procyonidae; plantigrade, scansorial) (Polly 2010; Polly et al. 2017). The gear ratio for Morphotype C (1.18; Table 5) is similar to that of Tremarctos ornatus (Cuvier, 1825) (Ursidae; Plantigrade, scansorial), Potos flavus (Schreber, 1774) (Procyonidae; plantigrade, arboreal) and Galictis vittata (Schreber, 1776) (Mustelidae; plantigrade, semi-fossorial) (Yensen & Tarifa 2003; Polly 2010; Polly et al. 2017). Morphotypes A and C may therefore correspond to plantigrade amphicyonids. Morphotype B has a more proximal sustentaculum tali, as in F. catus and L. rufus (Polly 2008). In addition, its morphology is close to that of the calcaneus of Daphoenodon robustum, which is digitigrade as indicated above (Hunt 2009). It also resembles the specimen of the Miocene digitigrade Plithocyon ursinus Cope, 1875 in North America (Paleontological Collection of MNHN), which also has a proximal sustentaculum tali and a distally long plantar tubercle. On the other hand, the peroneal process is well broad and the sustentaculum tali is located a little more dorsally, which seem to be plantigrade features (e.g., A. fulgens; Polly 2008). Even if the sustentaculum tali is more proximal than the other morphotypes, it is still far distal relative to extant digitigrade carnivorans (e.g., F. catus; Polly 2008). The gear ratio for Morphotype B is 1.25 (Table 5), which is close to P. lotor (semi-digitigrade, scansorial), Martes americana (Turton, 1806) (Mustelidae; plantigrade, scansorial) and Conepatus chinga (Molina, 1782) (Mephitidae; semi-digitigrade, terrestrial) (Polly 2010; Polly et al. 2017). Morphotype B would therefore rather be a semidigitigrade and terrestrial or scansorial animal, but probably not cursorial (gear ratio less than 1.22). The head of the astragalus of Cynodictis lacustris is inclined with respect to the mediolateral axis and the tendinous groove seems to merge with the trochlea, as in the digitigrade Urocyon cinereoargenteus (Schreber, 1775) (Wang 1993). However, the neck is quite short and the astragalar ectal facet is well curved, as in F. catus and L. rufus which are digitigrade and scansorial. In addition, the sustentaculum tali of the calcaneus is not placed very distally, as can be observed in a digitigrade animal (e.g., C. lupus; Polly et al. 2017). The gear ratio is 1.27 for C. lacustris (Table 5), which is similar to Vulpes vulpes (Linnaeus, 1758) (Canidae; digitigrade, terrestrial), Canis latrans Say, 1823 (Canidae; digitigrade, terrestrial), Canis rufus Audubon & Bachman, 1851 (Canidae; digitigrade, terrestrial), and Panthera onca Linnaeus, 1758 (Felidae; digitigrade, scansorial) (Polly et al. 2017). The canid species (i.e., Canis Linnaeus, 1758 and Vulpes Frisch, 1775) are all cursorial (Polly et al. 2017). Therefore, Cynodictis lacustris can be considered as digitigrade and cursorial. Interpretations are more contentious regarding locomotion. Based on the model of Polly & MacLeod (2008), the calcaneus of Cynodictis morphology is intermediate between the terrestrial and the scansorial morphologies. Morphotypes A and C are between the arboreal and terrestrial morphologies. But the specimens used for the implementation of this model are all extant animals and, in the case of plantigrady, the majority of the specimens are arboreal. Therefore, Polly & MacLeod���s (2008) model links plantigrady and arborality. While it is true that arboreal animals are often plantigrades (Taylor 1989; Panciroli et al. 2017), plantigrades are not necessarily arboreal (W, Published as part of Fournier, Morgane, Ladev��ze, Sandrine, Verger, K��vin Le, Fischer, Valentin, Speijer, Robert P. & Sol��, Flor��al, 2020, On the morphology of the astragalus and calcaneus of the amphicyonids (Carnivora, Mammalia) from the Paleogene of Europe: implications for the ecology of the European bear-dogs, pp. 305-325 in Geodiversitas 42 (18) on pages 316-320, DOI: 10.5252/geodiversitas2020v42a18, http://zenodo.org/record/3952805, {"references":["ZACK S. P. & ROSE K. 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Cynodictis lacustris Gervais, 1852 (Fig. 2) HOLOTYPE. ��� Fragmentary mandible bearing P4 and M1; MNHN. F.Qu unnumbered (Gervais 1852). NEWLY REFERRED SPECIMENS. ��� Astragali. MNHN.F.Au1076, MNHN.F.Au3169, MNHN.F.Au847, MNHN.F.Au3186I, MNHN.F.Au984, MNHN.F.Au994, unnumbered specimen (astragalus + navicular). Calcanei. MNHN.F.Au2188, MNHN.F.Au2699, MNHN.F.Au1059*, MNHN.F.Au848, MNHN.F.Au2398, MNHN.F.Au2020, MNHN.F.Au991, MNHN.F.Au2044, MNHN.F.Au2118*, MNHN.F.Au618, MNHN.F.Au822, MNHN.F.Au2209*(10), MNHN.F.Au2705, MNHN.F.Au2703, MNHN.F.Au992, MNHN.F.Au976, MNHN.F.Au2471, MNHN.F.Au845, MNHN.F.Au2391, MNHN.F.Au2018, MNHN.F.Qu9699, MNHN.F.Qu9757. STRATIGRAPHIC DISTRIBUTION. ��� MP18-MP21 Priabonian ��� early Rupelian. It should be noted that some authors suggest that the genus is present up to MP23 (e.g., Kotsakis 1980: 268, 269). TYPE LOCALITY. ��� La D��bruge (Vaucluse, France). LOCALITY. ��� Aubrelong (Lot, France). AGE LOCALITY. ��� MP21, early Rupelian. REMARKS ON NEWLY REFERRED SPECIMENS These specimens are here identified as Amphicyonidae because of their morphological similarities with European and North American amphicyonids: astragalus with a medial projection of the head and the asymmetry of the trochlea; calcaneus with a rounded shape of the sustentacular facet and a slight tilt in a medioproximal-laterodistal orientation of the cuboid facet. Futhermore, the differences observed with other carnivoran clades found in the Quercy deposits (Table 1) allow us to differentiate the studied bones from these taxa, and to support the assignment to amphicyonids. The specimens are assigned to the species C. lacustris because of their geographic localization, small size, and high relative abundance (see Comparison for determination). ASTRAGALUS (TALUS) DESCRIPTION (FIG. 2 A-E) Dorsal view The trochlea (trochlea tali proximalis) is deeply excavated. Its proximodistal length is greater than its mediolateral length. The axis of elongation of the trochlea is inclined relative to that of the neck. Its medial and lateral lips are of approximately the same proximodistal length and are more or less parallel. The proximal plantar tuberosity is very small or absent. The neck (collum tali) is mediolaterally thinner than the head (caput tali) and is relatively short. The head is strongly distally convex. It is broad (wider than the mediolateral length of the trochlea) and projected on the medial side. It rises on the neck on the medial side of the astragalus and almost reaches the distal edge of the trochlea. Ventral view The ectal facet (facies articularis calcaneae lateralis) is proximodistally elongated and more distally distinct than proximally. It is strongly concave and its medial edge curves slightly. The sinus of the tarsus (sinus tarsi) is deep. It clearly separates the two facets for the articulation with the calcaneus (facies articulares calcaneae). The sustentacular facet (facies articularis calcaneae medialis) is quite large and occupies a large portion of the width of the neck. Its medial and distal edges are well marked. It is elongated and extends proximomedially towards the trochlea. The distolateral part of this facet extends to almost reach the head of the astragalus (caput tali). It is slightly convex except on its proximomedial extension, where it becomes concave. The foramen in the proximal portion of this sinus is present. The head has a small ventral extension that goes partly back to the sustentacular facet. Lateral view A slight depression is formed proximal to the fibular facet (facies malleolaris lateralis). The proximomedial edge of the fibular facet forms a nearly right angle with the distal edge. The distal edge is relatively distally convex in the extension of the lateral edge of the trochlea. The ectal facet is well curved. Distal view The trochlea is slightly asymmetrical. The head is dorsoventrally flattened, thinner on the medial side, and wider on its lateral side. The axis of elongation of the head is inclined relative to the mediolateral axis of the astragalus. The lateral process is limited in breadth, forming only a slight medially directed tip. Proximal view The trochlear foramen is present on some specimens and absent in others. The proximoventral edge of the medial lip of the trochlea forms a slight ventral tip. The plantar tendon groove (for the flexor digitorum fibularis) is very weak. It seems to be fused with the proximal prolongation of the trochlea. The trochlea is mediolaterally thinner on its proximal part than on its dorsal part. CALCANEUS DESCRIPTION (FIG. 2 F-J) Dorsal view The medial process of the tuber calcanei is slightly proximally broader than the lateral process. The sagittal groove is rather marked. The tuber calcanei is not very mediolaterally broad but rather proximodistally elongated. The ectal facet (facies articularis talaris proximalis) is proximodistally elongated. It is strongly convex in the middle and very slightly proximally and distally concave. Its medial and lateral edges are slightly curved. The edges of this facet are rather well marked, except the distal edge, which merges with the body of the calcaneus and therefore is difficult to delimit. The sustentacular facet (facies articularis talaris distalis) is slightly elongated in the proximolateral-distomedial direction and extends slightly on the proximal edge of the sustentaculum tali. This gives a rather oval shape to this articular surface. The peroneal process is quite broad. The cuboid facet (facies articularis cuboidea) is inclined with respect to the mediolateral axis and its lateral edge rises above the body of the calcaneus. Lateral view The dorsal and ventral edges of the tuber are very slightly curved; the tuber is dorsoventrally wide. A well marked ridge is formed at the continuity of the peroneal process and join more distally the tuber calcanei. Medial view The groove for the plantar tendon (sulcus tendinis musculus flexor digiti lateralis) is pronounced. The plantar tubercle is distally large, forming a distally oriented tip. Distal view The cuboid facet is very slightly concave, quite dorsoventrally thin and mediolaterally elongated. The plantar tubercle is ventrally broad. The edge separating these two structures is not very broad. Proximal view The distal part of the tuber calcanei has a rather oval surface that is slightly dorsoventrally elongated. A slightly curved groove is ventrally clearly visible. COMPARISON These tarsal elements are all from Aubrelong (France, MP21; except two specimens whose exact locality is unknown). Cynodictis lacustris differs from Hyaenodonta (e.g., Hyaenodon Laizer & Parieu, 1838 from the Eocene of Europe [Bastl 2012] and Galecyon chronius Zack, 2011 from the Eocene of North America [Zack & Rose 2015]) in its astragalus morphology which displays an astragalar neck that is less distomedially oriented and mediolaterally thinner; a head that extends less on the medial part of the neck, and a medial edge of the head that is more pronounced (Table 1). Moreover, the plantar tendon groove is less pronounced than the proximal plantar tuberosity and the lateral process is slenderer than in Hyaenodonta. For the calcaneus, the cuboid facet of C. lacustris is less inclined than in Indohyaenodon raoi Bajpai, Kapur & Thewissen, 2009 (Ypresian, India; Rana et al. 2015) and Galecyon chronius (Eocene, North America; Zack & Rose 2015). Compared to Nimravidae, such as Hoplophoneus primaevus (Leidy & Owen, 1851) and Nimravus brachyops (Cope, 1878) (Oligocene, North America; Barrett 2016), the astragalus of C. lacustris has a longer neck and the head extends less on the medial side of the neck. Its calcaneus has a thinner sustentaculum tali and a shallower plantar tendon groove than in Nimravidae. Compared to Miacidae such as Vulpavus Marsh, 1871 (Eocene, North America; Heinrich & Rose 1997), the tarsal bones of C. lacustris are smaller, the neck of the astragalus is shorter and less medially projected, and the plantar tendon groove is less pronounced and less dorsally extended. Moreover, the sustentaculum tali is not as medially broad and proximally located, and the cuboid facet is less inclined. Cynodictis lacustris differs from Ursoidea (only modern forms because of the lack of ursid tarsal bones from the Paleogene or Miocene in the literature) (Gagnaison et al. 2017), such as Ursus spelaeus Rosenm��ller, 1794 (early Pleistocene of Europe; Santi et al. 2005) and Ursus arctos Linnaeus, 1758 (Pleistocene of Europe; Baryshnikov 2015): the astragalus of C. lacustris is thinner, the neck is much longer, and the trochlea is mediolaterally narrower and is not flattened proximodistally. The tuber calcanei is less stockier and mediolaterally thinner. The sustentaculum tali is less distally positioned and its sustentacular facet is shorter, more rounded, and not as inclined in the medioproximal-laterodistal direction. In comparison with Ailuridae, such as Simocyon batalleri (Viret, 1929) (Miocene, Spain; Salesa et al. 2008), the astragalus of C.lacustris has a shallower trochlea, a shorter and mediolaterally broader neck, and a less flattened head. The sustentaculum tali of the calcaneus is proximodistally thinner, the cuboid facet is more inclined and the plantar tendon groove is less marked than in S. batalleri. Compared with mustelids such as Martes sansaniensis Lartet, 1851, Ischyrictis zibethoides Blainville, 1841, and Taxodon sansaniensis Lartet, 1851 (Miocene, Europe; Peign�� 2012), the astragalar neck of C. lacustris is shorter and less medially projected and the sustentacular facet is mediolaterally broader. The calcaneus of C. lacustris has a more inclined cuboid facet and a shorter plantar tubercle than in M. sansaniensis. The sustentaculum tali is proximodistally and mediolaterally narrower, the tuber calcanei is mediolaterally thinner and the peroneal process is proximodistally broader than in T. sansaniensis. Cynodictis lacustris also exhibits a smaller calcaneus as compared with I. zibethoides, with a sustentaculum tali that is proximodistally narrower and a thinner medial process of tuber. All the features discussed above allow us to discriminate the Aubrelong amphicyonids from the other carnivorous groups recorded in Aubrelong and the Phosphorites du Quercy analysed in the framework of this study. The studied bones particularly resemble those of the Amphicyonidae, such as the European Amphicyon major Blainville, 1841 (Miocene) (Argot 2010) and the North American Amphicyon galushai Hunt, 2003 and Daphoenodon superbus Peterson, 1907 (Miocene) (Hunt 2009; 2011). In these four species, the head is mediolaterally broad and medially projected, while the trochlea is asymmetrical. Futhermore, the deep and relatively broad thochlea observed in C. lacustris is a characteristic of large amphicyonids according Gagnaison et al. (2017) as Amphicyon giganteus Schinz, 1825. Moreover, some differences are noticeable: for instance, the average length of the C. lacustris astragali (14.91 mm) is much less than the length of those of A. major, D. superbus and A. galushai (around 50 mm) and the neck in C. lacustris is more elongated than in the other two species. The morphology of the calcaneus of Cynodictis lacustris is close to that of Amphicyon major. In these two species, the medial process of the tuber calcanei is proximally longer than the lateral process, the sustentacular facet is prolonged on its proximal edge, the tuber calcanei is quite thick dorsoventrally, and the cuboid facet is inclined with respect to the mediolateral axis. However, the cuboid facet is more inclined and more concave, the peroneal process is less broad and the sustentaculum tali is more distally prolonged in Amphicyon major than in Cynodictis lacustris. The ratio of tarsal bone length/skull length of C. lacustris described here is similar to that of other amphicyonids. For instance, the ratio for Daphoenodon robustum Peterson, 1910 ranges between 0.14 to 0.16 for the astragalus and 0.24 to 0.26 for the calcaneus (Hunt 2009). In C. lacustris, the ratio for the astragalus ranges from 0.13 to 0.15 and for the calcaneus 0.18 to 0.26. This ratio is also close to that of modern ursids: 0.11 to 0.14 for the astragalus and 0.18 to 0.22 for the calcanueus (Baryshnikov & Boeskorov 2004; Baryshnikov 2015). Moreover, it is different from Hyaenodonta: astragalar ratio 0.09 to 0.11, and calcaneal ratio of 0.13 (Bastl 2012). In S. batalleri (Ailuridae), the astragalar ratio is 0.17 and the calcaneal ratio is 0.25. It is close to C. lacustris regarding the ı (Salesa et al. 2008). The lack of data in the literature prevents us from calculating ratios for other fossil carnivoran clades. Furthermore, the use of other criteria, such as relative abundance and size, allow us to be more specific and to attribute these tarsal bones to Cynodictis lacustris (Priabonian-Rupelian), primarily because this species is the only amphicyonid recognized based on dental and cranial elements in the Aubrelong locality (K. Le Verger pers. obs.). AMPHICYONIDAE Gen. indet. NEWLY REFERRED SPECIMENS. ��� Astragali. Morphotype 1: MNHN.F.Qu9986, MNHN.F.Qu10038, KUL.PLV1542.1, KUL. PLV1542_2, KUL.PLV1542_3, KUL.PLV1542_4. ��� Morphotype 2: MNHN.F.Qu10231, KUL.PLV1542_5, KUL.PLV1542_6, KUL.PLV1542_7, KUL.PLV1542_8. ��� Morphotype 3: MNHN.F.Qu9570, MNHN.F.Qu9758, MNHN.F.Qu10369, MNHN.F.Qu10368, MNHN.F.Qu10372, MNHN.F.Qu10371, MNHN.F.Qu10042, MNHN.F.Qu10367, ULgPA.17.175_1, ULgPA.17.175_2, ULgPA.17.175_3. ��� Morphotype 4: MNHN.F.Qu10039. Calcanei. Morphotype A: MNHN.F.Qu9845, MNHN.F.Qu10095, MNHN.F.Qu10230, MNHN.F.Qu10237, MNHN.F.Qu10284, MNHN.F.Qu10282, MNHN.F.Qu10344, MNHN.F.Qu10350, MNHN.F.Qu10349, MNHN.F.Qu10347, MNHN.F.Qu10351, ULgPA.17.170_1, ULgPA.17.170_2, ULgPA.17.170_3, ULgPA.17.170_4, ULgPA.17.170_5, ULgPA.17.170_6, ULgPA.1 7.1 70_7, UL gPA. 17. 170_ 8, U LgPA. 17. 170_9, ULgPA.17.170_10, ULgPA.17.170_11, ULgPA.17.170_12, ULgPA.17.170_13, ULgPA.17.170_14, ULgPA.17.170_15, ULgPA.17.170_16, ULgPA.17.170_17, ULgPA.17.170_18, ULgPA.17.170_19, KUL.PLV1542_9, KUL.PLV1542_10, KUL.PLV1542_11, KUL.PLV1542_12, KUL.PLV1542_13, KUL.PLV1542_14, KUL.PLV1542_15, KUL.PLV1542_16, KUL.PLV1542_17, KUL.PLV1542_18, KUL.PLV1542_19, KUL.PLV1542_20, KUL.PLV1542_21, KUL.PLV1542_22, KUL.PLV1542_23. ��� Morphotype B: MNHN.F.Qu10399, MNHN.F.Qu10005, MNHN.F.Qu10003, MNHN.F.Qu9775, MNHN.F.Qu10002, MNHN.F.Qu10381, MNHN.F.Qu10239, MNHN.F.Qu10346, MNHN.F.Qu9987, ULgPA.17.170_20, ULgPA.17.170_21, ULgPA.17.170_22, ULgPA.17.170_23, ULgPA.17.170_24, ULgPA.17.170_25, KUL.PLV1542_24, KUL. PLV1542_25, KUL.PLV1542_26, KUL.PLV1542_27, KUL. PLV1542_28. ��� Morphotype C: KUL.PLV1542_29. STRATIGRAPHIC DISTRIBUTION. ��� MP18-MP30; Priabonian-Chattian. LOCALITY. ��� Quercy (France), exact locality not indicated. REMARKS ON NEWLY REFERRED SPECIMENS These fossils are identified as Amphicyonidae because of their relative abundances, size, morphological similarities with European and North American amphicyonids and with C. lacustris described above, together with morphological differences from other carnivoran clades (Table 1). Moreover, relative abundance and body mass criteria support our identifications (see below). Although these bones are similar enough to those of amphicyonids to all be assigned to this family, morphological differences are noticeable between all these different specimens. These differences are perhaps representative of several amphicyonid genera or species, but so far more precise attribution is not possible, for lack of reliable arguments. For these reasons, they remain grouped into several morphotypes in this study, based on morphology and size (see Comparison for more details). ASTRAGALUS DESCRIPTIONS This set of astragalus morphotypes has the following characteristics. The trochlea is asymmetrical. Its mediolateral length is shorter than its proximodistal length. The axis of elongation of the trochlea is inclined relative to that of the neck. A depression is formed proximal to the fibular facet. The ectal facet is concave, proximodistally elongated and more distally thin. The sinus of the tarsus (sinus tarsi ��� sensu Schaller 2007) is deeply excavated. The sustentacular facet rises proximomedially towards the plantar tendon groove (for the flexor digitorum fibularis), as well as distolaterally to the head. This head is strongly distally convex and has a ventral extension that reaches back to the sustentacular facet.The head is dorsoventrally flattened, thinner on the medial side and wider on its lateral side. Four morphotypes are recognized among this sample of astragali due to differences in size and morphology., Published as part of Fournier, Morgane, Ladev��ze, Sandrine, Verger, K��vin Le, Fischer, Valentin, Speijer, Robert P. & Sol��, Flor��al, 2020, On the morphology of the astragalus and calcaneus of the amphicyonids (Carnivora, Mammalia) from the Paleogene of Europe: implications for the ecology of the European bear-dogs, pp. 305-325 in Geodiversitas 42 (18) on pages 310-313, DOI: 10.5252/geodiversitas2020v42a18, http://zenodo.org/record/3952805, {"references":["GERVAIS P. 1852. - Zoologie et paleontologie francaises (animaux vertebres) ou nouvelles recherches sur les animaux vivantes et fossiles de la France. Arthus Bertrand, Paris, 146 p. https: // doi. org / 10.5962 / bhl. title. 39473","KOTSAKIS T. 1980. - Revisione sistematica e distribuzione stratigrafica e geografica del genere Cynodictis Bravard & Pomel (Carnivora, Mammalia). 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