Bavarioboa aff. hermi Szyndlar & Schleich, 1993

Ivanov, Martin & Böhme, Madelaine, 2011, Snakes from Griesbeckerzell (Langhian, Early Badenian), North Alpine Foreland Basin (Germany), with comments on the evolution of snake faunas in Central Europe during the Miocene Climatic Optimum, Geodiversitas 33 (3), pp. 411-449 : 416-419

Bavarioboa aff. hermi Szyndlar & Schleich, 1993

MATERIAL EXAMINED. — 2 trunk vertebrae ( BSPG 1997 XIII 499, 500); 1 cloacal vertebra ( BSPG 1997 XIII 501).

LOCALITY. — Griesbeckerzell 1a.

DESCRIPTION

Trunk vertebrae ( Fig. 4A )

In lateral view, the more complete vertebra (BSPG 1997 XIII 499) is slightly higher than long. The neural spine is low and short, occupying about one third of the neural arch length. It was not possible to observe the typical dorsal thickening of the neural spine because the dorsal tip is not preserved, but we assume that at least in one vertebra the dorsal thickening was not developed. The lateral foramina are indistinct. The short interzygapophyseal ridges are sharp. The paradiapophyses are damaged; the subdivision into para- and diapophysis is indistinct. The diapophysis originally was much more smaller than the parapophysis. The relatively straight or slightly dorsally arched subcentral ridges are strongly developed and reach the condylar base. The ventral margin of the haemal keel is arched dorsally.

In dorsal view, the vertebrae are wider than long. The prezygapophyseal articular facets are subtriangular and elongated in lateral direction. Prezygapophyseal processes are not visible from above.The cranial margin of the zygosphene is almost straight; sometimes two small lateral lobes are developed.The base of the neural spine rises at the level of the posterior margin of the prezygapophyseal articular facets.The posterior end of the neural spine is widened. The interzygapophyseal constriction is moderately deep.

In ventral view, the centrum is slightly wider than long. The prominent haemal keel is limited by the deep subcentral grooves. Subcentral foramina are small and situated at the base of the anterior part of the haemal keel. The subtriangular to oval postzygapophyseal articular facets are strongly laterally elongated.

In cranial view, the zygosphene is straight and is either as wide as the cotyle or markedly wider. In one vertebra the zygosphenal lip is thickened. The cotylar rim is circular; paracotylar foramina in deep depressions are absent.

In caudal view, the neural arch is weakly vaulted, and the condyle is rounded and situated on a short neck. Measurements of the larger vertebra are as follows: cl = 5.37 mm; naw = 6.32 mm.; cl/naw = 0.85.

Cloacal vertebra ( Fig. 4B )

A single fragmentary vertebra is preserved with broken off prezygapophyses. Bases of the incipient haemapophyses occupy unusually anterior position. They are developed at the ventral margin of the haemal keel, which is typical for the cloacal region of the vertebral column.

DISCUSSION

Although paracotylar foramina are absent, the vertebrae can be assigned to the Boinae based on the relatively small dimensions (compared with Miocene Pythoninae Fitzinger, 1826 , e.g., Python europaeus Szyndlar & Rage, 2003 [cf. Ivanov 2000; Szyndlar & Rage 2003]) and several typical features of the genus Bavarioboa . The general morphology concurs with that of Bavarioboa , including the absence of dorsal thickening of the neural spine in the middle trunk vertebrae,the straight cranial margin of the zygosphene in cranial view, and the weakly vaulted neural arch (cf. Szyndlar & Rage 2003). Vertebrae of Bavarioboa aff. hermi resemble those of Bavarioboa hermi from the type locality Petersbuch 2, Germany (Early Miocene, late Eggenburgian) in the following features: 1) the cranial margin of the zygosphene is straight and small lateral lobes may occur; 2) the haemal keel is widened posteriorly, especially in one specimen of a posterior precaudal vertebra; and 3) the neural spine of trunk vertebrae is not thickened. However, the trunk vertebrae are somewhat lower compared to those of Bavarioboa hermi , but the neural spine is not as low as the neural spine of the late Early Miocene (Karpatian) Bavarioboa ultima Szyndlar &Rage,2003 from Rothenstein 13, Germany (cf. Szyndlar & Rage 2003). Morphologically, vertebrae of Bavarioboa aff. hermi from Griesbeckerzell 1a seem to occupy an intermediate position between the Early Miocene Bavarioboa hermi from Petersbuch 2 ( Germany) and Dolnice ( Czech Republic; Ottnangian) and the late Early Miocene Bavarioboa ultima from Rothenstein 13 ( Germany), which has been regarded as the

ct

last representative of the genus Bavarioboa in Europe ( Szyndlar & Rage 2003).

Figures

FIG. 4. — Bavarioboa aff.hermi from the Middle Miocene (MN 6, base) of Griesbeckerzell 1a in lateral (l), dorsal (d), ventral (v), cranial (cr), and caudal (ca) views:A, middle trunk vertebra (BSPG 1997 XIII 499);B, cloacal vertebra (BSPG 1997 XIII 501).Abbreviations:cd, condyle; ct, cotyle; hae, haemapophysis; hk, haemal keel; lf, lateral foramen; na, neural arch; nc, neural canal; ns, neural spine; pr, prezygapophysis; prf, prezygapophyseal articular facet; prp, prezygapophyseal process; po, postzygapophysis; pof, postzygapophyseal articular facet; scf, subcentral foramen; scr, subcentral ridge; syn, synapophysis; zy, zygosphene; zyg, zygantrum. Scale bar: 2 mm.