Coluber dolnicensis Szyndlar, 1987

Ivanov, Martin, 2002, The oldest known Miocene snake fauna from Central Europe: Merkur-North locality, Czech Republic, Acta Palaeontologica Polonica 47 (3), pp. 513-534 : 514-517

publication ID	https://doi.org/ 10.5281/zenodo.13286109
persistent identifier	https://treatment.plazi.org/id/8220878C-FFDB-FF86-FC83-C3FF19F44600
treatment provided by	Felipe
scientific name	Coluber dolnicensis Szyndlar, 1987
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Coluber dolnicensis ; Szyndlar 1987: 65–66, fig. 8.

Coluber dolnicensis Szyndlar ; Szyndlar 1991a: 115, fig. 10.

Coluber dolnicensis Szyndlar ; Ivanov 1997a: 45–46, fig. 24.

Material.—One left dentary ( SGDB Ah−12), 4 compound bones (3 left + l right) ( SGDB 7408/MI−9, 10; SGDB Ah−13, 14), 1 cervical vertebra ( SGDB Ah−15), 2 cervical vertebrae ( SGDB 7408/MI−5, 6), 23 trunk vertebrae ( SGDB 7408/MI−7–4; SGDB 7408/MI−92–95; SGDB 7408/MI−101), 19 trunk vertebrae ( SGDB Ah−16–32; SGDB Ah−613, 614), 1 caudal vertebra ( SGDB 7408/MI−25).

Dentary ( Fig. 3A View Fig 1 –A View Fig 2 View Fig ).—The bone is very fragmentary, the preserved rostral part is curved medially. The bone originally was probably massive and it is markedly thickened close to the symphysis which can be easily observed, especially in ventral view. The Meckel’s groove is completely enclosed at the level of the 6 th tooth. The mental foramen occurs at the levelofthe9 th and10 th teeth.Unfortunately,thecaudalpartof the dentary is not preserved, therefore it was not possible to determine either the precise position of the rostral termination of the compound notch or the number of tooth spaces.

Compound bone ( Fig. 3B View Fig 1 –B View Fig 2 View Fig , C).—In labial view, the lingual flange of the fossa mandibularis is twice high as the labial flange. The antero−dorsal margin of the lingual flange is distinctly steep. The labial flange is more or less rectilinear

and at the ventral border it is limited by the elongated supraangular crest which extends to the supraangular foramen. The supraangular foramen lies far from the rostral termination of the fossa mandibularis. Caudal parts of the bone with slender retroarticular process are preserved in two specimens. Adistinct large foramen occurs at the medial side of the base of the retroarticular process.

Cervical vertebrae ( Fig. 3D View Fig 1 –D View Fig 4 View Fig ).—The vertebrae are fragmentary with the neural spines broken off close to their base. The neural arch is slightly vaulted and the neural canal is rounded. The subcentral ridges are well developed and moderately arched dorsally. The paradiapophyses are distinctly divided; the diapophyses are directed postero−laterally, and they are about as large as the parapophyses. The parapophyseal processes are directed antero−ventrally. The lateral lobes of the zygosphene are well developed in dorsal view,

B A 2

E 2

E 3

D 2

D 3 F1 F2

the median lobe is not produced, thus the margin of the zygosphenal lip is slightly concave. The large prezygapophyseal articular facets are suborbicularly to irregularly shaped and the prezygapophyseal processes are very small (about 1/5 of the length of the prezygapophyseal articular facets) and pointed.

Trunk vertebrae ( Fig. 3E View Fig 1 –E View Fig 5 View Fig ).—In lateral view, the neural spine is about twice as long as high. The cranial margin of the damaged neural spine was probably vertical or overhanging anteriorly. The caudal margin of the neural spine clearly overhangs posteriorly. The interzygapophyseal ridges are well developed and distinct lateral foramina occur in depressions (which are sometimes relatively deep) slightly ventral to the ridges. Lateral foramina are obvious, especially from lateroventral view rather than in lateral view. The subcentral ridges are distinct and are straight or slightly arched dorsally. The haemal keel is terminated anteriorly by a distinct step. The parapophyses are separated from diapophyses and the diapophyses are as large as parapophyses or somewhat smaller. The parapophyseal processes are very short and rounded at their ventral margin. In dorsal view, the zygosphene is either straight or convex with distinct lateral lobes. The prezygapophyseal articular facets are widely oval and the prezygapophyseal processes are about two times shorter than the prezygapophyseal articular facets. The epizygapophyseal ridges are underdeveloped. In ventral view, the subcentral grooves are shallow. The haemal keel is separated from the area just posterior to the cotyle by a distinct step. Asmall subcotylar tubercle is sometimes also developed. In cranial view, the neural archismoderatelyvaultedandtheneuralcanalisroundedwith small lateral sinuses. The zygosphenal lip is straight to slightly convex. The paracotylar foramina lie in depressions on both sides of the circular cotyle. In caudal view, minute parazygantral foramina occur in some vertebrae just above the postzygapophyseal articular facets. Measurements are as follows (n = 21): cl: or = 4.10–5.40 mm; naw: or = 3.05– 4.01 mm; cl/naw: or = 1.20–1.50, mean l.37±0.09.

Caudal vertebra ( Fig. 3F View Fig 1 –F View Fig 3 View Fig ).—Avery fragmentary verte − bra has its neural spine, the pleurapophyses and the haemapophyses broken off just at their bases. The small lateral foramina occur in depressions just under the interzygapophyseal ridges. In dorsal view, the zygosphene has distinct lateral lobes and a wide median lobe. The prezygapophyseal articular facets are oval and the pointed prezygapophyseal processes are about half the length of the prezygapophyseal articularfacets.Theparacotylarforaminaaresmallandoccur indepressionsonbothsidesofthecotylewhichisslightlydepressed dorso−ventrally.

Comments.—The dentary of Coluber dolnicensis Szyndlar, 1987 is described for the first time here. Afragmentary com − pound bone was described earlier by Szyndlar (1987).

The fragmentary dentary was probably massive and the mental foramen is relatively long which allowed assignment to the genus Coluber . The bone differs from both the recent and fossil representatives of this genus by its massive structure in the proximity of the symphysis. This element is assigned to the species C. dolnicensis but assignment to some other species of the genus Coluber cannot be excluded.

The compound bone is referred to C. dolnicensis based on the general morphological resemblance to the type material from Dolnice, MN 4 ( Szyndlar 1987). The most diagnostic character is the presence of the prominent crest evolved from the elongated supraangular crest. This crest, unlike the material from Dolnice ( Szyndlar 1987), extends to the supraangular foramen.

On the basis of vertebrae alone, determination of fossil representatives of the subfamily Colubrinae is very difficult. Therefore, it is not often possible to identify this material to the species or even at the generic level without cranial bones. The absence of the hypapophyses on relatively long and slender vertebrae and the relatively low neural spines allow assignment of this material to the subfamily Colubrinae and to the genus Coluber . Fossil representatives of the genus Coluber are relatively common in the European Neogene including ( Szyndlar and Böhme 1993; Szyndlar and Schleich 1993; Bachmayer and Szyndlar 1985, 1987; Bolkay 1913; Venczel 1994, 1998): cf. “ Coluber ” cadurci Rage, 1974 (MN 1),? Coluber cadurci Rage, 1974 (MN 2), Coluber caspioides Szyndlar and Schleich, 1993 (MN 3a, this paper – MN 4), Coluber dolnicensis Szyndlar, 1987 (MN 3a, this paper – MN 4), Coluber sansaniensis Lartet, 1851 (MN 6), Coluber suevicus ( Fraas, 1870) (MN 3a, this paper – MN 7+8), Coluber planicarinatus ( Bachmayer and Szyndlar, 1985) (MN 11) and Coluber hungaricus ( Bolkay, 1913) (MN 13).

The trunk vertebrae from Merkur−North are most similar to the species C. dolnicensis . Cervical vertebrae are describedinthisextinctspeciesforthefirsttimeanddifferfrom the cervical vertebrae of other species by the slender parapophyseal processes that project under the vertebral centrum. Very short prezygapophyseal processes in trunk vertebrae are rare in the genus Coluber . Trunk vertebrae of C. dolnicensis differ from living and extinct members of the genus Coluber by the prominent step in anterior part of the haemal keel and by the diapophyses, which are shifted far behind the parapophyses ( Szyndlar 1987). The caudal vertebra, although very fragmentary, is assigned to the species C. dolnicensis on the basis of the general shape of the zygosphenal lip, the presence of the distinct interzygapophyseal ridgesandlateralforaminawhicharesituatedindepressions.