Albanerpeton inexpectatum Estes & Hoffstetter 1976
Makaleler > Tam Makale · 2021
Yazarlar: Georgalis, Georgios L., Čerňanský, Andrej, Serdar MAYDA
, Uluslararası, 2021
Özet
Albanerpeton cf. inexpectatum (Fig. 2) MATERIAL. — Turkey. Kavakdere:a premaxilla (EUNMH PV 14053) and a left dentary (EUNMH PV 14057). DESCRIPTION Premaxilla The premaxilla EUNMH PV 14053 is a robustly constructed, paired element (Fig. 2A, B); the left one is present in the available material (note that Gardner [1999a] reported that small sized premaxillae are paired, whereas larger are fused, suggesting its later fusion during ontogeny). The nasal process is broad, moderately high. The sculpture in the dorsal portion of the process (dorsal boss) exhibits a pustulate irregular ornamentation. Here, the process is slightly laterally constricted due to a presence of a lateral facet for the nasal. The ventrally located labial portion of the nasal process is rather smooth. This portion is pierced by external nutritive foramina (sensu Gardner 1999a) of various sizes (in overall, the foramina more or less decrease in size dorsally). The large wedge-shaped facet for maxilla is developed on the labial side of the short maxillary process. The supradental shelf (sensu Rage & Augé 2010) is well-developed. The premaxilla bears seven tooth positions. However, only the first four teeth (counted from median plane) are in better condition. The internal portion of the nasal process base is pierced by a suprapalatal pit (sensu Gardner 2002). This pit is moderate in size, dorsolaterally bordered by internal strut. The suture with the right premaxilla is well visible in posterior aspect. Dentary The left dentary EUNMH PV 14057 is partially preserved (Fig. 2 C-E). The otherwise smooth labial surface of the preserved portion is pierced by two labial foramina. In lingual aspect, the high dental crest supports 17 tooth position (12 teeth are still attached plus two anterior ones have preserved their ventral portions). The Meckel’s groove is closed, only partly exposed in the posterior section of the dentary. The subdental shelf (sensu Rage & Augé 2010) is straight, well medially expanded especially in the anterior section. However, the anterior end of the dentary is broken off and missing. The posterior portion is damaged, but the posterodorsal process (called “unnamed process” by Gardner 2002) is preserved directly behind the tooth row, being short, blunt and low (not distinctly dorsally elevated). The rest of the posterior region is broken off and missing. Dentition The tooth implantation is pleurodont. The teeth are conical, not pedicellate. The tooth crowns are smooth and do not contrast with tooth necks. The dentary teeth gradually increase in size anteriorly. The tooth crowns, when are preserved, show some degree of tricuspidity (angulus mesialis and distalis are present). The sizes of inter-dental gaps are roughly half those of the tooth bases. The tooth bases lack resorption pits. COMMENTS The morphology of both Kavakdere specimens fits well with albanerpetontids, a clade of middle Jurassic to early Pleistocene extinct lissamphibians, which were chameleon-like ballistic feeders (seeDaza et al. 2020). They have a mainly documented Laurasian distribution (Gardner 1999a, 1999b, 2002; Venczel & Gardner 2005; Delfino & Sala 2007; Matsumoto & Evans 2018; Villa et al. 2018), although it is noted that they are also reported from Morocco as well (Gardner et al. 2003) and finds from the Cretaceous Myanmar amber might also point towards a Gondwanan distribution (see Daza et al. 2020). The new material described herein resembles more particularly the genus Albanerpeton, found in North America and Europe (however, see Discussion). The Kavakdere material represents the first evidence of this extinct clade in Turkey as well as its easternmost European occurrence. More precisely, our material shares two diagnostic characters with the type species of the genus, Albanerpetoninexpectatum (see Gardner 1999a): 1) a presence of the pustulate ornamentation of the dorsal section of the premaxillary nasal process; and 2) the presence of a small, low posterodorsal process behind the tooth row. The Pliocene Albanerpeton pannonicus Venczel & Gardner, 2005 differs from the new Kavakdere material in, e.g.: 1) nasal process of premaxilla short; 2) short dorsal boss of premaxilla on labial surface occupying about upper one third or less of the nasal process; 3) absence of the posterodorsal process behind the tooth row; and4) having only weakly heterodont teeth in anterior half of the dentary regarding their size (see Venczel & Gardner 2005; Delfino & Sala 2007).