Bavarioboa cf. hermi, Szyndlar & Schleich, 1993

Vasilyan, Davit, Cernansky, Andrej, Szyndlar, Zbigniew & Moers, Thomas, 2022, Amphibian and reptilian fauna from the early Miocene of Echzell, Germany, Fossil Record 25 (1), pp. 99-145 : 99

Bavarioboa cf. hermi

Fig. 18A-E

Material.

Forty-two trunk vertebrae HLMD-Ez 2146-2148, one cloacal vertebra HLMD-Ez 2149, four caudal vertebrae HLMD-Ez 2150 and HLMD-Ez 2150a.

Description.

Trunk vertebrae: All but one trunk vertebrae come from the middle trunk portion of the column. Some of them are preserved in relatively good condition, perhaps due to their robust morphology as characteristic of constrictors. In lateral view, these vertebrae are as high as long. In dorsal and ventral views, they are distinctly wider than long. In the largest and best-preserved vertebra HLMD-Ez 2148, the centrum length measures 5.7 mm, centrum width - 7.2 mm, centrum length/centrum width equals 0.8. The interzygapophyseal constriction, especially in larger vertebrae, is weakly expressed. The centrum is subtriangular in shape. The haemal keel is prominent, broad and slightly broadening posteriorly. In a few vertebrae, however, the keel looks like a biconcave lens owing to the presence of a distinct constriction, located at the level of the subcentral foramina, and prominent broadenings at the anterior and posterior ends. The subcentral grooves and subcentral ridges are prominent. The neural arch is moderately depressed. The neural spine is very low (approximately three times longer than high), thick, and widening posteriorly (Fig. 18A ). It occupies more than one half the length of the neural arch and begins immediately behind the zygosphenal articular facets. The zygosphenal roof is slightly convex or roughly straight in dorsal view. The prezygapophyseal and postzygapophyseal articular facets are usually subsquare in shape. The prezygapophyseal processes (if preserved) are very short and hardly visible dorsally. The paradiapophyses are subsquare in outline, higher than long, with indistinct subdivision into para- and diapophyseal portions. The cotyle and condyle are slightly flattened. The subcentral and lateral foramina are large. The paracotylar foramina are absent (Fig. 18D ).

In the sole anterior trunk vertebra HLMD-Ez 2146, the haemal keel is replaced by a ventrally directed hypapophysis (its distal portion is broken). The neural spine of this vertebra is very short and relatively high in lateral view. Apart from these characteristics, the anterior trunk vertebra does not differ significantly from the middle trunk vertebrae.

Cloacal vertebra: One cloacal vertebra HLMD-Ez 2149, as characteristic for the sacral portion of the column, is provided with paired lymphapophyses (their distal ends are broken). The centrum length measures 3.4 mm, centrum width - 4.1 mm, centrum length / centrum width equals 0.8. Surprisingly, located on the ventral side of the centrum, minute but distinct paired haemapophyses are present, thus far the trait unknown in the genus Bavarioboa (see below).

Caudal vertebrae: Four caudal vertebrae are provided with paired pleurapophyses (missing or partly missing in some vertebrae). In the largest caudal vertebra HLMD-Ez 2150, the centrum length is 4.0 mm, centrum width 4.5 mm, centrum length / centrum width 0.9. Situated on the ventral side of the centrum, are short but distinct paired haemapophyses (partly broken).

Remarks.

The constrictor from Echzell displays clearly diagnostic features of the genus Bavarioboa , so among others: mid-trunk vertebrae distinctly wider than long; the interzygapophyseal constriction well expressed; the neural arch moderately depressed; the neural spine approximately as high as long, occupying one half the length of the neural arch; the haemal keel prominent; the zygosphene usually roughly straight; the prezygapophyses located clearly above the floor of the neural canal; the long axis of prezygapophyseal facets oblique in dorsal view; the prezygapophyseal processes weakly developed; the paradiapophyses subsquare in shape, with indistinct subdivision into para- and diapophyseal portions ( Szyndlar and Rage 2003). By their morphological characteristics and also relatively large size, the vertebrae are similar to those of the type species, Bavarioboa hermi , occurring in the German and Czech late early Miocene ( Szyndlar and Schleich 1993; Szyndlar and Rage 2003; Ivanov et al. 2020). However, the peculiar hourglass-shaped haemal keels observed in a few trunk vertebrae suggest affinities with Bavarioboa crocheti from the French late Oligocene. Interestingly, the sole mid-trunk vertebra of Bavarioboa reported from Turkey by Szyndlar and Hoşgör (2012) was provided with a similar (i.e., Bavarioboa crocheti -like) keel. Nonetheless, other morphological traits of the vertebrae from Echzell suggest that the snake represented Bavarioboa hermi or a closely related form.

There is yet another strange anatomical peculiarity observed in the sole cloacal vertebra of Bavarioboa from Echzell, namely the presence of the paired haemapophyses. This is surprising, because, in virtually all recent genera of the Boinae , haemapophyses are absent in the sacral region of the column as well as they are absent in the anterior caudals. Exactly the same morphological pattern was observed in some species of Bavarioboa , whose vertebrae coming from the sacral / anterior caudal portion of the column of which were available ( Szyndlar and Rage 2003). However, there is at last one exception from this tendency in the Boinae , namely, the presence of haemapophyses was confirmed in the posterior cloacal vertebrae (as well in the anterior caudals) in the living boine Epicrates cenchria (Szyndlar, unpublished observation).

Figures

Figure 18. Snakes from the Echzell. A-E. Bavarioboa cf. hermi (HLMD-Ez 2148), middle trunk vertebra; F-J. " Colubrinae " indet. (HLMD-Ez 2159), middle trunk vertebra; K, L. Naja cf. romani (HLMD-Ez 2151), middle trunk vertebra. All vertebrae in (A, F, K) lateral, (B, G, L) dorsal, (C, H, M) ventral, (D, I, N) anterior and (E, J, O) posterior views.