Glanochthon, Schoch and Witzmann, 2009

Schoch Correspondence, Rainer R., 2021, Osteology of the Permian temnospondyl amphibian Glanochthon lellbachae and its relationships, Fossil Record 24 (1), pp. 49-64 : 58-63

Glanochthon . In the present analysis, S. haeuseri was confined to Boy’s subspecies S. haeuseri haeuseri .

6 Conclusions

Sclerocephalus was the most common and regionally widespread genus in the lower Rotliegend of the Saar –Nahe Basin, and morphological change through the rock sequence was considerable (Schoch, 2009, 2014; Schoch and Witzmann, 2009a). This was already highlighted by Boy (1988) who paid tribute to the morphological change across stratigraphic levels. He formally defined S. bavaricus and S. haeuseri as chronospecies and recognized two chronosubspecies within the latter: S. haeuseri jeckenbachensis from Lake Jeckenbach (M6) and S. haeuseri haeuseri from Lake Pfarrwald (M9-P). Throughout the sequence A1–M8, there was only a single taxon present at any preserved time slice.

Before deposition of the M9 sequence, Sclerocephalus probably formed an anagenetic lineage spanning some 2 Myr (A1–Q1–M3–M6–M8) as there is no evidence of cladogenesis within the Saar –Nahe Basin. However, the phylogenetic placement of S. jogischneideri between S. bavaricus and S. sp. Concordia suggests the emigration of a post-A1 population which ultimately appeared in the Thuringian Forest (southwest Saale) Basin. This placement was already suggested by Werneburg (1992). The age of S. jogischneideri (upper Oberhof Formation) relative to that of the Saar –Nahe Basin sequence is controversial but probably not older than M9 and possibly much younger ( Lützner et al., 2012).

In M9, where two different lakes existed that were separated by a tectonic structure (Kappeln M9-K in the north, Pfarrwald M9-P in the south), morphologically distinct samples appear. Whereas Lake Pfarrwald harbored classical S. haeuseri ( S. haeuseri haeuseri of Boy, 1988), Lake Kappeln was inhabited by an apparently uniform population similar to S. haeuseri in the southwest (St. Wendel locality S-2 of Boy, 1987, clay pit Halseband, and road cut nearby) but two distinct taxa in the northeast (Odernheim and Alsenz regions), here referred to as S. nobilis and G. lellbachae . The latter two are likely to have diverged within the time interval between the M8 and M9 lake deposits and, as indicated by phylogenetic analysis, evolved from S. haeuseri , which is well-known from M8 deposits. These interesting patterns will be analyzed elsewhere.

Speaking within the framework of Boy’s chronospecies concept, the ancestor of S. nobilis and G. lellbachae branched off after S. h. jeckenbachensis and before S. h. haeuseri . As Boy (1988) noted, S. h. haeuseri had evolved a narrow interorbital region and slender posterior skull table, which was considered a derived character of later S. haeuseri ( Schoch et al., 2019) . However, these features are unique to the population in Lake Pfarrwald, which falls within M9 rather than M10 as originally considered by Boy (1988), a fact that became only apparent after more research had been conducted (Boy et al., 2012). The subsequent, true M10 population of S. haeuseri from the lowermost horizons of Lake Humberg (Odernheim region) differs from the M9-P Pfarrwald population (S. h. haeuseri ), instead sharing more aquatic features with M8 S. haeuseri (Schoch, 2009) . Hence, Pfarrwald S. haeuseri is more likely to form a regionally isolated population, whereas M10 S. haeuseri more likely evolved from a population in Lake Kappeln, such as the one preserved in the M9-K sample from St. Wendel.

A more detailed assessment of the relationships between all species referred to Sclerocephalus will be carried out elsewhere. In the present cladogram, phylogenetic positioning might be hypothesized as being influenced by size disparity and ontogenetic disparity, with S. stambergi and S. jogischneideri both found to be basal and relatively small taxa. In contrast to the rather adult morphology of S. jogischneideri , S. stambergi has an immature appearance, probably representing a juvenile, by analogy with the ontogenetically wellsampled S. haeuseri ( Boy, 1988) . Furthermore, both S. jogischneideri and S. stambergi are known from a single specimen each, whereas the other taxa or samples (“populations”) are represented by dozens or sometimes hundreds of specimens (Schoch, 2009; Krätschmer, 2004), and some stratigraphically (and probably phylogenetically) younger samples (Lake Odernheim, M8; Lake Humberg, M10) are known by small, paedomorphic adults only (Schoch, 2009). Furthermore, as large adults are very rare, they are often found only after many years of continued collecting. Admittedly, this fact also weakens the size disparity between S. nobilis and G. lellbachae mentioned above.

Phylogenetic analysis indicates that G. lellbachae forms the stratigraphically oldest taxon of the Glanochthon clade, sharing a range of synapomorphies with its stratigraphically younger relatives G. angusta (M10c) and G. latirostre (M10d). The three taxa might well form an anagenetic lineage, but speciation events cannot be ruled out. The two different hypotheses can only be tested by more detailed geographic and stratigraphic sampling, which is hardly possible without numerous new additional outcrops.

A new, still to be formally named species of Glanochthon was reported by Steyer (1996) from BuxiŁres-les-Mines (Allier basins, France). Boy and Schindler (2012) and Schnei- der and Werneburg (2012) concur that the corresponding rock unit, the Membre supØrieur of the Assise de BuxiŁres- Autunien gris ( Steyer et al., 2000), falls within the uppermost part of the Meisenheim Formation. This is consistent with the proposed hypothesis of an origin of Glanochthon within the Saar–Nahe Basin and a subsequent emigration into the Allier basins.

The current phylogenetic findings are not readily translated into a taxonomic scheme. The easiest solution would be to grant each sample from a different lake deposit a separate species name. This is practiced here in the straightforward case of Glanochthon , but in the vast series of samples of Sclerocephalus haeuseri , Boy’s (1988) chronosubspecies approach still remains more appealing. A morphometric study analyzing this interesting problem is under way and will be published elsewhere. Provided that the findings of the present study are correct, Sclerocephalus forms a paraphyletic assemblage with respect to the Glanochthon clade. The logical and phylogenetically correct approach would be to erect new genera for the successive species, but the close resemblance of most of these taxa would make these difficult to define. The extraordinary detailed stratigraphic and morphological record of the Sclerocephalus – Glanochthon clade therefore demonstrates the limits of any taxonomic approach to classify evolving lineages.

Appendix A: Character list

1. Premaxilla (alary process). Absent (0) or present (1).

2. Premaxilla (prenarial portion). Short (0) or expanded anteriorly by about the length of the naris (1).

3. Premaxilla (outline). Parabolically rounded (0) or box-like, anteriorly blunt (1).

4. Snout (internarial distance). Narrower than interorbital distance (0) or wider (1).

5. Snout (margin). Straight (0) or laterally constricted at level of naris (1).

6. Rostrum. Absent (0) or present (1).

7. Internarial fenestra. Absent (0) or present (1).

8. Orbits. Round to slightly oval (0) or elongated oval (1).

9. Orbits. Ends rounded (0) or pointed (1).

10. Maxilla (anterior margin). Straight (0) or laterally convex due to enlarged teeth (1).

11. Maxilla (contact to nasal). Absent, separated by lacrimal (0) or present (1).

12. Nasal (lateral margin). Straight (0) or stepped with lateral excursion anterior to prefrontal, accommodating narrower lacrimal (1).

13. Lacrimal (length). As long as nasal (0), shorter than nasal (1) or much abbreviated (2).

14. Lacrimal (width). Lateral suture parallels medial one (0) or lateral suture posterolaterally expanded to give broader preorbital region (1).

15. Preorbital region (length). Less than twice the length of posterior skull table (0) or more (1).

16. Prefrontal-jugal (contact). Absent (0) or present (1).

17. Prefrontal (anterior end). Pointed (0) or wide and blunt (1).

18. Frontal-nasal (length). Frontal as long or longer than nasal (0) or shorter (1).

19. Interorbital distance. Narrower than orbital width (0) or wider (1).

20. Lateral line (sulci). Absent in adults (0) or present (1).

21. Posterior skull table (length). Less than 0.7 times the width (0), 0.7–0.8 times (1) or larger than 0.8 (2).

22. Intertemporal. Present (0) or absent (1).

23. Postorbital. Long triangular, wedged deeply between squamosal and supratemporal (0) or short (1).

24. Squamosal embayment (size). Wide, giving semilunar flange on squamosal (0) or slit-like with thin flange on squamosal (1).

25. Tabular (ventral crest). Absent (0) or present (1).

26. Jugal (preorbital expansion). Absent in adults (0) or present (1).

27. Ornament. Polygons and short ridges (0) or long ridges arranged radially (1).

28. Vomer. Smooth (0) or with paired depressions anteriorly (1).

29. Vomerine tusks. Anterolateral to choana, transverse row (0) or well anterior to choana, sagittal row (1).

30. Anterior palatal openings. Absent (0) or present (1).

31. Choana (width). Elongated oval or slit-like (0) or round (1).

32. Premaxilla. Borders choana (0) or not (1).

33. Palatine, ectopterygoid (continuous tooth row). Absent (0) or present (1).

34. Palatine. Fangs and no more than 3–4 extra teeth (0) or 5 or more extra teeth (1).

35. Ectopterygoid (tusks). Present (0) or absent (1).

36. Parasphenoid. Denticle field on plate triangular (0) or round (1).

37. Basipterygoid ramus (length). Transverse, rod-like (0) or short without medial extension (1).

38. Basicranial articulation. Moveable overlap (0) or tightly sutured (1).

39. Carotid foramina (entrance). Anteromedial on basal plate, close to cultriform process (0) or at posterolateral corner of plate (1).

40. Vomer. Separated by pterygoid from interpterygoid vacuity (0) or bordering that opening (1).

41. Cultriform process (width). Throughout of similar width (0) or posteriorly expanding abruptly to about twice the width (1).

42. Stapes (quadrate process). Absent (0) or present (1).

43. Interclavicle (adult shape). As wide as long (0) or longer than wide (1).

44. Interclavicle (width). As wide or wider than posterior skull table (0) or narrower (1).

45. Interclavicle (size). Shorter than posterior skull table (0) or longer than half of skull length (1).

46. Interclavicle (posterior margin). Triangular, pointed (0) or rounded to blunt (1).

47. Interclavicle (outline). Rhomboid (0) or quadrangular to pentagonal (1).

48. Humerus (entepicondylar foramen). Present (0) or absent (1).

49. Humerus (supinator). Present (0) or absent (1).

50. Humerus. Short with slow growth rate in larvae (0) or long due to rapid growth (1).

51. Femur. Intercondylar fossa on dorsodistal surface forming deep trough (0) or shallow groove (1).

52. Pubis. Ossified (0) or unossified (1).

53. Ilium. Shaft kinked, posteriorly directed (0), shaft straight and dorsal with broadened end (1), or shaft straight posterodorsally directed (2). Unordered.

54. Ribs. Short (0), long rod-like with small uncinates (1) or long with blade-like uncinates (2). Unordered.

55. Interpterygoid vacuities. Longer than vomer and premaxilla (0) or equal to or shorter (1).

56. Neurocranium. Cartilaginous or only partially ossified (0) or fully ossified with sphenoid and ethmoid portions (1).

57. Squamosal embayment. Framed by parallel squamosal and tabular margins (0) or forming medially rounded extension, constricting the posterior skull table (1).

58. Supratemporal. Less than or about 2 times longer than wide (0) or more than 2 times longer than wide (1).

59. Squamosal. Posterior part as wide as quadratojugal (0) or markedly narrower (1).

60. Jugal. Wider than orbit (0) or markedly narrower (1).

61. Premaxilla. Lateral margin straight (0) or bulging laterally (1).

62. Snout. Shorter than 2 times the length of postorbital skull table (0) or as long as or longer (1).

63. Lacrimal. At least two-thirds the length of the preorbital skull (0) or shorter (1).

64. Quadrate. Wedging in between quadratojugal and squamosal posteriorly (0) or offset from the posterior margin of the dermal cheek bones (1).

Appendix B: Character–taxon matrix

Dendrysekos_helogenes

1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0

0 0 0 0? 0 0 0 0 0 0 0 0 0 1 0 0 0 0

Balanerpeton_woodi

1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0

Cochleosaurus_bohemicus

0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Micromelerpeton_credneri

1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0

1 1 1 1 1 0 0 1 0 1 0 0 0 0 1 0 0 0 0

Acanthostomatops_vorax

1 1 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 1 0 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0

1 1 1 0 1 0 1 2 0 1 0 0 0 0 0 0 0 0 0

Iberospondylus_schultzei

1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0?? 0 0????

??????? 1 1 0 0 0 0 0 0 0 0 0

Eryops_megacephalus

1 0 1 1 0 0 0 0 0 1 0 0 0 1 1 1 1 1 1 0 0 1 1 1 0 1 0 1 0 0 1 0 0 0 0 0 0 1 1 1 1 0 0 0 0

1 0 1 0 0 1 0 2 2 0 1 0 0 0 0 0 0 1 0

Onchiodon_labyrinthicus

1 0 1 1 0 0 0 0 0 1 0 0 0 1 1 1 1 0 1 0 0 1 1 1 0 1 0 1 0 0 1 0 0 0 0 0 0 1 1 1 1 0 0 0?

1 0 1 0 0 1 0 2 2 0 0 0 0 0 0 0 0 0 0

Actinodon _frossardi

1 0 1 1 0 0 0 0 0 0 0 0 0 0 1 1 0 0 1 0 0 1 0 1 0 1 0 1 0 0 0 0 0 0 0 0 0 1 1 1 1? 0 0 1

1 0 1 0? 1 0? 2 0 0 0 0 0 0 0 0 0 0

“ Sclerocephalus ” _stambergi

1 0 1 1 0 0 0 0 0 0 1 1 1 0 0 1 0 0 0? 2 1 0 1 1 1 0??????????????? 1 1 1??????????? 0 0 0 0 0 0 0 0

Sclerocephalus_bavaricus

1 1 0 1 0 0 0 0 0 0 1 1 2 0 0 1 0 0 0 1 2 1 0 1 1 1 0 1 0 0 0 0? 0 0 0 0 0 1 1 0? 1 0 1 0 0 1? 0 1? 1 2?? 0 0 0 0 0 0 1 1

Sclerocephalus_haeuseri

1 0 1 1 0 0 0 0 0 1 1 2 2 0 0 1 0 0 0 0 2 1 0 1 1 1 0 1 0 0 0 0 1 0 0 0 0 0 1 1 0 1 1 0 1 0 0 1 0 0 1 0 1 2 1 0 1 0 0 0 0 0 1 1

Sclerocephalus _sp._Concordia

1 0 1 1 0 0 0 0 0 1 1 2 2 0 0 1 0 0 0 0 2 1 0 1 1 1 0 1 0 0 0 0 1 0 0 0 0 1 1 1 0 1 1 0 1 0 0 1 0 0 1? 1 2 0 1 0 0 0 0 0 0 1 1

Sclerocephalus_jogischneideri

1 0 1 1 0 0 0 0 0 1 1 2 2 0 0 1 0 0 0 1 2 1 0 1 1 1 0 1 0 0 0 0 1 0 0 0 0 0 1 1 0? 1 0 1 0 0 1? 0 1? 1 2 1 0 0 0 0 0 0 0 1 1

Sclerocephalus_nobilis

1 1 1 1 0 0 0 0 0 1 1 2 1 0 0 1 0 0 0 0 2 1 0 1 1 1 0 1 0 0 0 0 1 0 0 0 0 0 1 1 0? 1 0 1 0 0 1 0 0 1 0 1 2 1 0 1 1 1 0 0 1 1 1

Glanochthon_lellbachae

1 1 1 1 1 0 0 0 1 1 1 1? 0 1 1 0 0 0 1 2 1 0 1 1 1 0 1 0 0 0 0 1 0 1 0 0 0 1 1 0 0 1 1 1 0 0 1 1 0 1 0 1 1 1 0 0 1 1 1 0 1 1 1

Glanochthon_angusta

1 1 1 1 1 0 0 0 1 1 1 1? 0 1 1 0 0 0 1 2 1 0 1 1 1 0 1 0 0 0 0 1 0 1 0 0 0 1 1 0 0 1 1 1 0 0 1 1 0 1 1 1 1 1 0 0 1 1 1 1 1 1 1

Glanochthon_latirostre

1 1 1 1 1 0 0 0 1 1 1 1 1 0 1 1 0 0 0 1 1 1 0 1 1 1 1 1 0 0 0 0 1 0 1 0 0 0 1 1 0 0 1 1 1 0 0 1 1 0 1 1 1 1 1 0 0 1 1 1 1 1 1 1

Intasuchus_silvicola

1 1 0 1 0 0 0 1? 0 0 0 0 0 1 1 0 1 0? 0 1 0 1? 1 1 1 0 0 0 1 1 1 1 0 1 0 1 1 0????????????? 1 0 0 0 0 0 0 0 0 0

Melosaurus_uralensis

1 1 0 1 0 0 0 1 0 0 1 0 0 0 1 1 0 1 0? 1 1 0 1? 1 0??????????????? 1 1? 0?? 1????? 1 0 0 0 0 0 0 0 0 0

Cheliderpeton_vranyi

1 0 0 1 0 0 0 0 0 0? 0 0 0 0 1 0 1 0 1 2 1 0 1? 1 0??????????????? 1 0 1 0 0 1 1 0 1 1 2 1 1 0 0 0 0 0 0 0 0 0

Archegosaurus_decheni

1 1 0 1 0 1 0 1 0 0 1 0 0 0 1 1 0 1 0 1 2 1 0 1 1 1 1 1 1 0 0 1 1 1 1 1 1 0 1 1 0 1 1 1 1 0 0 1 1 0 1 1 1 1 1 0 0 0 0 1 0 0 0 0

Platyoposaurus _stuckenbergensis

1 1 0 1 0 1 0 0 0 0 1 0 0 0 1 1 0 1 0 1 2 1 0 1 1 1 0 1 1 1 0 1 1 1 1 1 1 0 1 1 0 0 1 1 1 0 0 1 1? 1 1 1 1 1 0 0 0 0 0 0 0 0 0

Australerpeton_cosgriffi

1 1 0 1 0 1 0 0 0 0 1 0 0 0 1 1 0 1 0 1 2 1 0 1 1 1 0 1 1 1 0 1 1 1 1 1 1 1 1 1 0 0 1 1 1 0 0 1 0? 1 1 1 1 1 0 0 0 0 0 0 0 0 0

Code availability. Software package available under: https:// cladistics.org/tnt (Willi Hennig Society, 2021).