Early Miocene squamate assemblage from the Mokrá-Western Quarry (Czech Republic) and its palaeobiogeographical and palaeoenvironmental implications Author Ivanov, Martin Author Čerňanský, Andrej Author Bonilla-Salomón, Isaac Author Luján, Àngel Hernández text Geodiversitas 2020 2020-08-28 42 20 343 376 journal article 8562 10.5252/geodiversitas2020v42a20 ad4dbfb6-14ce-48e2-8fe9-99fa26a9bcf4 1638-9395 4447563 urn:lsid:zoobank.org:pub:8FF2A078-CE45-4BF1-A681-00136F57375E Python sp. ( Fig. 8 ) Boidae gen. et sp. indet. (large form) – Ivanov & Musil 2004: 228 , 229, fig. 3A, B. Boidae gen. et sp. indet – Ivanov et al. 2006: 229 , table 2. MATERIAL. — MWQ, early Miocene, Burdigalian, Orleanian, MN 4: 1/2001 Turtle Joint: two trunk vertebrae (Pal. 1449, 1450). DESCRIPTION Trunk vertebrae The more complete middle trunk vertebra (Pal. 1449) has lost the left prezygapophyseal facet as well as the lateral extension of the left postzygapophysis. In lateral view, the vertebra is anteroposteriorly shorter than high. The strongly vaulted neural arch is caudally upswept above the zygantrum. The neural spine has a gently eroded dorsal margin and is slightly longer than high. Its cranial margin is vertical and rises in the middle of the zygosphene length. The caudal margin of the neural spine is inclined posteriorly behind the neural arch. The interzypapophyseal ridges are rather sharp. The zygosphenal surfaces are wide and irregularly oval. They are characterised by conspicuously large dimensions. The lateral foramina are large, and they sit in shallow depressions. The haemal keel is arched upwards. In dorsal view, the wide zygosphene possesses distinct lateral lobes; the damaged medial lobe was rather small. The neural spine is thick. The right prezygapophyseal articular facet is subtriangular. The prezygapophyseal process is rather short and it is hardly visible from the dorsal aspect. The interzygapophyseal constriction is shallow. The neural arch widens triangularly in a caudal direction. The median notch, developed at the caudal margin of the neural arch, reaches anteriorly as far as the cranial margin of the postzygapophysis. In ventral view, the paradiapophyses are massively developed. The large right postzygapophyseal articular facet has a subtriangular outline and is laterally elongated. In this view, the haemal keel is relatively wide with subcentral foramina situated at both sides of its base. In cranial view, the relatively thin prezygapophyses are tilted slightly dorsally with their base situated just above the floor of the neural canal. The lateral extension of the preserved right postzygapophysis is conspicuously thin. The neural arch is strongly vaulted, and the neural canal is rounded with short lateral sinuses. The straight cranial margin of the zygosphene is thick along its entire width. Deep depressions occur on either side of a large cotyle of almost circular outline. Paracotylar foramina are absent. In caudal view, the zygantrum is large and laterally wide. The postzygapophyses are tilted dorsally like the prezygapophyses. Several very small foramina are arranged in a line on caudal side of both postzygapophyses. The condyle is almost circular with a depressed ventral margin. The vertebral dimensions are as follows: larger specimen (Pal. 1449): cl = 7.32 mm ; naw = 10.39 mm ; cl /naw = 0.70. Smaller specimen (Pal. 1450): cl = 5.45 mm ; naw = 8.15 mm ; cl/naw = 0.67. REMARKS The following combination of features indicate assignment of the better preserved vertebra to the extant genus Python (see Szyndlar & Rage 2003 ): 1) the large vertebra is massively built with cl/naw ratio <1; 2) the absence of paracotylar foramina; 3) the caudal section of the strongly vaulted neural arch is upswept above the zygantrum; and 4) the zygosphenal roof is thick in anterior aspect. The markedly developed sharp subcentral ridges indicate that this vertebra was situated close/or within the posterior section of the trunk region. Python sp. from MWQ particularly resembles the only known extinct Python species, Python europaeus Szyndlar & Rage, 2003 , reported from French early Miocene Béon 1 (MN 4) and Vieux-Collonges (MN 5) localities ( Szyndlar & Rage 2003 ; Rage & Bailon 2005 ), and from the middle Miocene (MN 6, base) of Griesbeckerzell 1a, Germany ( Ivanov & Böhme 2011 ). However, Python sp. from MWQ differs from P. europaeus by the following features: 1) the zygosphene of Python sp. is not straight – conspicuous lateral lobes are present; 2) in cranial view, the zygosphenal lip is slightly less massive compared to that of P. europaeus ; and 3) lateral extensions of postzygapophyses are more slender than the same structures in P. europaeus . The trunk vertebrae of Python sp. from MWQ are smaller than middle trunk vertebrae of P. europaeus ( Szyndlar & Rage 2003 ) . As the morphology and build of the zygosphene strongly depends on the ontogenetic stage, it is possible that vertebrae of Python sp. belonged to subadult specimens.