Coluber suevicus ( Fraas, 1870 )

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 : 517-522

publication ID	https://doi.org/ 10.5281/zenodo.13286109
persistent identifier	https://treatment.plazi.org/id/8220878C-FFDE-FF8B-FC83-C3A31E404746
treatment provided by	Felipe
scientific name	Coluber suevicus ( Fraas, 1870 )
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Treatment

Coluber suevicus ( Fraas, 1870)

Naja suevica ; Fraas 1870: 291.

? Coluber suevica (Fraas) ; Rage 1984: 45.

Coluber suevicus (Fraas) ; Szyndlar and Böhme 1993: 405, fig. 7. Coluber suevicus (Fraas) ; Ivanov 1997a: 48, fig. 25. Material.—One right quadrate (SGDB Ah−33), 3 cervical vertebrae (SGDB Ah−34–36), 11 trunk vertebrae (SGDB 7408/MI−26–36), 7 trunk vertebrae (SGDB Ah−37–43).

Quadrate ( Fig. 4A View Fig ).—In postero−lateral view, this massive boneexpandstowardthedorsalcrest.Thedorsalcrestismark−

B 2

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C 2

edly thickened on its entire length. Asmall distinct and ven − trally directed process occurs on the antero−medial margin of the dorsal crest. The distinct quadrate crest is high and sharp, its distal termination missing as well as a part of trochlea quadrati. The stapedial process is strongly damaged.

Cervical vertebrae ( Fig. 4B View Fig 1 –B View Fig 3 View Fig ).—These vertebrae are fragmentary with hypapophyses broken off close to their base. The neural arch is weakly vaulted, the neural canal is rounded. The dorsally thickened neural spine is about as long ashighandbothitscranialandcaudalmarginsarebifurcated. The cranial margin of the neural spine slightly overhangs anteriorly and the caudal margin overhangs posteriorly. The parapophyses are as large as the diapophyses or somewhat smaller and the parapophyseal processes are short and directed anteriorly. The zygosphene has lateral lobes; the median lobe is short and wide and sometimes it is absent. The hypapophysis extends proximally up to the ventral margin of cotylewheretheprominentsubcotylartuberclesaresituated.

Trunk vertebrae ( Fig. 4C View Fig 1 –C View Fig 5 View Fig ).—In lateral view, the neural spine is often broken off; if preserved, it is about twice as long as high and its cranial margin distinctly overhangs anteriorly and caudal margin overhangs posteriorly. In the largest vertebrae, a dorsal thickening of the neural spine may develop. The sharp interzygapophyseal ridges are prominent. The lateral foramina are distinct and they occur in deep depressions just ventral to the interzygapophyseal ridges. The subcentral ridges are short (especially in the largest vertebrae) and arched dorsally. The paradiapophyses are indistinctly divided and the parapophyses are longer than the postero−laterally directed diapophyses. In dorsal view, the zygosphene is straight or concave with distinct lateral lobes. The prezygapophyseal articular facets are conspicuously broad in the largest vertebrae, are oval or irregularly shaped and the prezygapophyseal processes of the largest vertebrae are very short (about three times the length of the prezygapophyseal articular facets) and obtuse. In smaller vertebrae the prezygapophyseal facets are smaller than the blunt prezygapophyseal processes which are longer. The epizygapophyseal spines are moderately developed. In ventral view, the distinct blunt haemal keel expands posteriorly and its ventral margin is more or less flattened. The haemal keel continues anteriorly toward the base of the cotyle. The distinct subcotylar tubercles are developed at the cotylar base of the largest vertebrae. Subcentral foramina are obvious and they occur just atthe base orclose tothe base ofthe haemal keel. The postzygapophyseal articular facets of the largest vertebrae are enlarged laterally. In cranial view, the neural arch is moderatelyvaulted.Theneuralcanalisroundedandhasshortdistinct lateral sinuses. Sometimes prominent nerve foramina occur at the base of the prezygapophyseal processes just belowthearticularfacets.Theparacotylarforaminaaresituated in deep depressions on both sides of the rounded or laterally slightly depressed cotyle. The parapophyseal processes are very short and their ventral margins are slightly below the level of subcotylar tubercles. Measurements are as follows (n = 9): cl: or = 4.14–6.44 mm; naw: or = 3.01–4.66 mm; cl/naw: or = 1.31–1.42, mean 1.36±0.03.

Comments.—The quadrate undoubtedly represents the genus Coluber based on the expanding body of the bone, the prominent dorsal crest and the small stapedial process. Unlike the recent and fossil representatives, including Coluber caspioides Szyndlar and Schleich, 1993 , the area of the dorsal crest is markedly thickened and the bone is much more massively built. The quadrate is identified as belonging to Coluber suevicus ( Fraas, 1870) based on its large size on the basis that vertebrae of this species belong to the largest colubrine snakes discovered at Merkur−North.

These vertebrae (cervical vertebrae are reported for the first time) certainly belong to a large snake of the genus Coluber ; the material of trunk vertebrae especially resembles C. suevicus that was known only from the German Middle Miocene (MN 7+8) type locality at Steinheim ( Rage 1984; SzyndlarandBöhme1993:407,fig.7).Trunkvertebraefrom Merkur−North do not essentially differ in morphology from the German discoveries of C. suevicus , although the prezygapophyseal processes figured by Szyndlar and Böhme (1993) seem to be more pointed. C. suevicus from Merkur−North resembles the German specimens of this species mainly by having: 1, the same shape and relative size of the pre− and postzygapophyseal articular facets; 2, the same development of the haemal keel; 3, the presence of distinct subcotylar tubercles; 4, the very short parapophyseal processes whose ventral margin extends only slightly below the level of the subcotylar tubercles. The shape and location of the parapophyseal processes differentiates C. suevicus from other known fossil and recent representatives of the genus Coluber .

Coluber caspioides Szyndlar and Schleich, 1993 Coluber caspioides ; Szyndlar and Schleich 1993: 23–26, fig. 6.

Material.—One left frontal ( SGDB Ah−44), 1right pterygoid ( SGDB Ah−45), 1 right palatine ( SGDB Ah−46), 1 right quadrate ( SGDB Ah−11), 2 (left + right) dentaries ( SGDB Ah−47, 48), 2 right compound bones ( SGDB Ah−49, 50), 8 cervical vertebrae ( SGDB Ah−51–58), 14 trunk vertebrae ( SGDB 7408/MI−37–50), 110 trunk vertebrae ( SGDB Ah−59–166; SGDB Ah−615, 616), 1 cloacal vertebra ( SGDB Ah−167).

Frontal ( Fig. 5A View Fig 1 –A View Fig 2 View Fig ).—The bone is very fragmentary and only the dorsal part of the bone is preserved. In dorsal view, the rostral part of the bone expands laterally and the orbital margin is slightly turned up. Both the external and internal premaxillary processes are of equal size and the external process is more rounded that the internal one. In rostral view, the distal end of the distinct internal premaxillary process is markedly rounded.

Palatine ( Fig. 5B View Fig ).—This fragmentary palatine has the complete maxillary process with its wide base preserved. The maxillary process lies at the level of the 5 th –6 th teeth. The vomerine process is broken off. The postero−labially directed maxillary process has a large maxillary nerve foramen at its base. Because the material is incomplete it is not possible to estimate the number of teeth; only two caudally directed teeth are preserved.

Pterygoid ( Fig. 5C View Fig 1 –C View Fig 2 View Fig ).—The fragmentary right pterygoid lacks rostral and caudal parts. In dorsal view, the distinct pterygoid crest can be seen and the pterygoid flange is prominent at the caudal end of the ectopterygoid process. Unfortunately, the rostral part of the ectopterygoid process is damaged. On the ventral side, the bone retains fragmentary tooth row with 5 tooth sockets (only three sockets are complete).

Quadratum ( Fig. 5D View Fig ).—In postero−lateral aspect, this gracile bone becomes wider toward the dorsal crest. The distinct quadrate crest extends from the dorsal crest to the proximity of the trochlea quadrati. The dorsal crest is only moderately thickened at its antero−medial part. The stapedial process is small and only indistinctly separated from the body of the bone.

Dentary ( Fig. 5E View Fig ).—These bones are fragmentary and their caudal parts are broken off. The rostral part becomes thinner distally just anterior the mental foramen and is curved medially. Meckel’s groove is completely enclosed at the level of the 5 th tooth. The mental foramen is long and occurs at the level of the 9 th (in one bone?10 th) – 11 th tooth. From the mental foramen a marked groove extends in rostral direction. The notch for the rostral termination of the compound groove is relatively sharp and is situated at the level of the 15 th tooth. The precise number of the teeth (or teeth sockets) remains unknown.

Compound bone ( Fig. 5F View Fig 1 View Fig , F 2 View Fig ).—The rostral part of this fragmentary bone is missing and the retroarticular process is broken off at its distal end. In labial view, the labial flange of the mandibular fossa is about 1.5–2 times lower than the lingual flange. The labial flange is concave dorsally and the ventral margin of this concavity forms an enlarged ridge extending from the well developed supraangular crest. This ridge terminates close to the distinct supraangular foramen that lies far from the rostral end of the mandibular fossa. A low but distinct crest occurs on the lingual side of the bone and extends from the base of the retroarticular process to the proximity of the dorsal margin of the lingual flange of the mandibular fossa.

Cervical vertebrae ( Fig. 5G View Fig 1 –G View Fig 5 View Fig ).—The neural arch is vaulted and the neural canal is rounded with shallow lateral sinuses. The neural spine is somewhat longer than high with indistinct dorsal thickening and the neural spine overhangs slightly anteriorly, more distinctively posteriorly. The paradiapophyses are well divided, the diapophyses are longer than the parapophyses and the gracile parapophyseal processes are directed anteriorly. The pointed distal end of the hypapophysis is directed postero−caudally. The subcentral ridges are long and moderately arched dorsally. The zygosphene has well developed lateral lobes and the median lobe is wide, indistinct, or missing. The prezygapophyseal articular facets are rounded to oval and the prezygapophyseal processes are very short and pointed. The small paracotylar foramina occur in depressions on both sides of the rounded cotyle.

Trunk vertebrae ( Fig. 5H View Fig 1 View Fig , H 2 View Fig , I 1 –I View Fig 5 View Fig ).—In lateral view, the neural spine is about 1.5 times longer than high, its cranial margin slightly overhangs anteriorly and the caudal margin overhangs caudally. The interzygapophyseal ridges are well developed and the lateral foramina are conspicuous and situated in shallow depressions. The dorsally slightly arched subcentral ridges are well developed and do not reach the cotylar rim. The haemal keel is relatively deep and gradually decreases at about 1/3 of the bone length towards the cotyle. The parapophyses are not distinctly separated from the diapophyses and the diapophyses are somewhat smaller than the parapophyses. The parapophyses are rounded on the ventral side. In dorsal view, the zygosphenal lip has distinct lateral lobes. Although usually distinct, the median lobe can be eitherunderdevelopedorabsentandhasashallowmedianincision. The prezygapophyseal articular facets are subtriangular to oval, the prezygapophyseal processes are somewhat shorter than the prezygapophyseal facets and they are directed antero−laterally. The epizygapophyseal spines are missing. In ventral view, the blunt subcentral ridges are relatively well developed and the subcentral grooves are wide and shallow. The conspicuous subcentral foramina lie close to the base of the haemal keel. The postzygapophyseal articular facets are irregularly shaped. In cranial view, the neural arch is moderately vaulted and the neural canal is rounded with shallow lateral sinuses and the zygosphenal lip is convex or straight. Nerve foramina occur at the bases of the prezygapophyseal processes. The paracotylar processes occurindepressionsonbothsidesoftheroundedcotyle.Incaudal view, minute parazygantral foramina are present. Measurements are as follows (n = 26): cl: or = 3.10–5.57 mm; naw: or = 2.20–4.11 mm; cl/naw: or = 1.13–1.76, mean l.39±0.12.

Cloacal vertebra.—The vertebra is very damaged, the caudal margin of the neural spine overhangs posteriorly and the cranial margin is unpreserved. The lymphapophyses are broken off at their bases. Asuggestion of the division of the haemal keel into the haemapophyses can be observed. In dorsal view, the zygosphene has distinct lateral lobes and the wide and blunt median lobe is obvious. The zygosphenal lip is convex in cranial view.

Comments.—Cranial elements are assigned to Coluber caspioides Szyndlar and Schleich, 1993 for the first time but we cannot exclude a doubtful assignment of some cranial bones, not only because of the fragmentary condition of the fossil material, but also because several species of the genus Coluber occur in the locality. Aconsiderable number of the fossil vertebrae of the genus Coluber most likely belong to C. caspioides .

Theassignmentofthefrontaltothegenus Coluber isbased on the presence of the prominent internal and external premaxillary processes and also on the general shape of the bone which has a wide rostral area. The long internal premaxillary process is markedly rounded in both dorsal and rostral views, which distinguishes C. caspioides from remaining known recent and fossil species of the genus Coluber .

Thepalatineisassignedtothegenus Coluber basedonthe presence of a prominent pointed maxillary process with a wide base. The bone is very similar to the palatine of the extant species C. caspius based on the conspicuous maxillary nerve foramen.

Avery fragmentary pterygoid bone is assigned to the ge − nus Coluber based on the presence of a distinct pterygoid crest and ectopterygoid process. The bone especially resembles the pterygoid of the living species C. viridiflavus as both

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the pterygoid crest and short pterygoid flange are more distinctive in C. caspioides .

The quadrate bone is typical of the genus Coluber based on its enlarged body near the dorsal crest and the small stapedial process. Unlike the recent representatives, the bone is somewhat shorter and wider. The trochlea quadrati is massively built and is less twisted against the dorsal crest unlike the recent and the known fossil representatives. Unfortunately, we cannot exclude assignment of the quadrate to another member of the genus Coluber .

The dentary resembles the genus Coluber on the basis of theshapeandthepositionofthementalforamenandthelevel of enclosure of the Meckel’s groove. C. caspioides differs from all known recent and fossil representatives based on the distinct groove extending from the mental foramen to the rostral end of the bone.

The compound bone is assigned to the genus Coluber on the presence of the distinct supraangular crest and concave labial flange of the mandibular fossa. The labial flange is comparatively high as in the living C. caspius . It was not possible to see the orientation of the broken off retroarticular process, therefore, a more precise comparison with other representatives of this genus is not possible. The presence of a low but distinct crest on the lingual side of the bone distinguishestheextinctspecies C. caspioides fromothermembers of the genus Coluber .

The assignment of vertebrae to C. caspioides , reported originally from the Early Miocene (MN 4) type locality at Petersbuch 2 ( Germany), is based on the morphological resemblance to this species ( Szyndlar and Schleich 1993). Vertebrae from Merkur−North, originally identified as belonging to Colubrinae A( Ivanov 1997a: 94, fig. 41), resemble the material from Petersbuch 2 especially on the shape of the neural spine and the haemal keel. However, there are several differences:thevertebraefromMerkur−Northaresmallerand the cranial margin of the zygosphene is crenate from above and convex in cranial view. On the other hand, the zygosphene of C. caspioides from Petersbuch 2 is straight with a shallow incision in dorsal view and also straight in cranial view. These differences are probably only a result of intraspecific morphological variability because the largest vertebrae of C. caspioides from Merkur−North are quite similar to the material from Petersbuch 2.

According to Szyndlar and Schleich (1993), C. caspioides could be a member of the lineage leading to the recent species C. caspius , however, most of the reported cranial bones of the extinct C. caspioides differ significantly from the living representatives of the genus Coluber (including C. caspius ). Therefore, assuming that the referral of cranial bones to the species is accurate, it seems to be more probable that C. caspioides is a member of a different, perhaps separate, lineage.