Cheliderpeton lellbachae Krätschmer, 2006

Schoch Correspondence, Rainer R., 2021, Osteology of the Permian temnospondyl amphibian Glanochthon lellbachae and its relationships, Fossil Record 24 (1), pp. 49-64 : 51-55

Cheliderpeton lellbachae Krätschmer, 2006

Holotype

NHMM 2006 / 14, 102 mm SL, complete skeleton with skin impression ( Fig. 2 ).

Type of locality and age

The Klauswald southwest of Odernheim am Glan, Rhineland-Palatinate, Germany ( Fig. 1 ). M9 sequence, Klauswald facies, Odernheim Subformation, Meisenheim Formation, lower Rotliegend, Autunian, lowermost Permian.

Referred material

Altogether, five additional specimens are referred to as Glanochthon lellbachae (see material section). There remains a substantial number of specimens in private collections.

Diagnosis

Autapomorphies: (1) preorbital region in adults 1.8– 2.0 times as long as postorbital skull table, (2) dermal ornament with continuous and relatively tall radial ridges in the snout, frontals and cheek (contrasting the more polygonal arrangement in S. nobilis ), (3) prefrontal anterolaterally expanded to form a more equant pentagon, (4) squamosal posteriorly only half as wide as quadratojugal, (5) phalanges of manus and pes slightly longer and more gracile than in S. nobilis and (6) tail substantially longer than skull and trunk combined (shorter than that measurement in S. nobilis ).

Taxonomic assignment

This taxon was originally erected as Cheliderpeton lellbachae by Krätschmer (2006), who made reference to its resemblance to Cheliderpeton latirostre as described and referred to by Boy (1993). Schoch and Witzmann (2009b) suggested the new genus name Glanochthon for Cheliderpeton latirostre after the type species Cheliderpeton vranyi had been redescribed by Werneburg and Steyer (2002) and was found not to be closely related to G. latirostre ( Schoch and Witzmann, 2009b) . Based on its below-demonstrated close relationship to G. latirostre , Cheliderpeton lellbachae is also referred to as Glanochthon as a new combination.

G. lellbachae co-occurs with Sclerocephalus nobilis in the same locality and horizon ( Krätschmer and Resch, 2005; Schoch and Witzmann, 2009a). The combined list of autapomorphic characters 1–5 for the genus distinguish this taxon from S. nobilis and all other species of Sclerocephalus . Hypothetical larvae and small juveniles of G. lellbachae and S. nobilis may not be distinguished on the basis of the mentioned features, but S. nobilis generally has a wider jugal and more rounded orbit even at small stages. The presence of a third eryopiform temnospondyl at the Klauswald locality (suggested by Krätschmer, 2006) cannot be confirmed. With a maximum skull length of 17 cm (specimens in private collections), G. lellbachae appears to have been smaller than the more heavily ossified S. nobilis (24 cm), but admittedly the number of available specimens is very limited.

R. R. Schoch: Osteology of the Permian temnospondyl amphibian Glanochthon lellbachae 55

Phylogeny and taxonomy

In the analysis reported below, S. nobilis and the Glanochthon clade are found to be sister taxa. This recognized topological pattern leads to the phylogenetically problematic situation that Sclerocephalus forms a grade towards Glanochthon , which under strict application of cladistic principles would prompt erection of new genera at each node. An alternative option would be to define Sclerocephalus more broadly, encompassing all of Sclerocephalidae including Glanochthon . At the present stage, I consider any such step premature as long as morphological effects of microevolution cannot be distinguished from other effects, especially plasticity (ecophenotypes), which is beyond the scope of the present study.

Comment

Based on the current phylogenetic findings, Glanochthon is referred to as the family Sclerocephalidae , which contains a monophyletic group including a long Sclerocephalus grade and a terminal Glanochthon clade. The former referral of Glanochthon (as Cheliderpeton latirostre ) within the Intasuchidae ( Schoch and Milner, 2000) was based on a suite of characters which appear to be convergent in the present light of evidence.

Occurrence

Although S. nobilis and G. lellbachae co-occur in the same locality and several successive horizons, they differ in sample size per horizon. Most notably, G. lellbachae is more common in the upper fish beds (Obere Fischschiefer, “kalkige Papierschiefer”, K5), whereas S. nobilis peaks in the lower fish beds (Untere Fischschiefer, K2) as defined by Krätschmer (2004). In the other beds (K3, 4), the two taxa co-occur, mostly represented by large juveniles.

Figures

Figure 1. Localities yielding Sclerocephalus and Glanochthon material and stratigraphy of the Rotliegend sequence with emphasis on the Meisenheim Formation (Autunian, Lower Permian) in the Saar–Nahe Basin of Germany.

Figure 2. Type specimen of Glanochthon lellbachae (Krätschmer, 2006) comb. nov. (NHMM 2006/14). (a, c) Close-up of skull roof and (b) complete skeleton.