Phalarodon atavus ( Quenstedt, 1851 –1852)

Sues, Hans-Dieter & Schoch, Rainer R., 2025, Synopsis of the Triassic reptiles from Germany, Fossil Record 28 (2), pp. 411-483 : 411-483

Phalarodon atavus ( Quenstedt, 1851 –1852)

Lectotype.

GPIT-PV -60575 , cranial fragment with almost complete left maxilla, lacrimal, and incomplete prefrontal ( Maisch and Matzke 2001).

Lectotype locality.

Calw-Althengstett, Baden-Württemberg.

Lectotype horizon.

Dornstetten Subformation, Freudenstadt Formation, Lower Muschelkalk Subgroup. Age: Middle Triassic (Anisian: Bithynian-Pelsonian).

Referred material.

See Maisch and Matzke (2001). F. Huene (1916) first published an incomplete cranium ( SMNS 15378 ) from the Lower Muschelkalk Subgroup near Simmozheim in the Calw district, Baden-Württemberg. Edinger (1935 b) described a well-preserved partial cranium ( MB. R. 2325 ; Fig. 9 B ) from an unspecified horizon of the Upper Muschelkalk Subgroup at Rüdersdorf near Berlin, Brandenburg.

Diagnosis.

Distinguished by the following combination of features: most large and fully developed teeth with deep groove on roots; dental groove absent along entire tooth-bearing jaw margin; dentition homodont, with conical teeth; ventral margin of scapula straight; and metacarpal V larger than distal carpal 4 ( Maisch and Matzke 2000; Liu et al. 2013). The cranium of Phalarodon atavus also has a particularly prominent sagittal crest ( Motani 1999 b; Maisch and Matzke 2001; Fig. 9 B ).

Comments.

Maisch and Matzke (1998) considered the type material of “ Ichthyosaurus ” atavus inadequate for taxonomic purposes but later ( Maisch and Matzke 2001) selected GPIT-PV -60575 as the lectotype. F. Huene (1916) classified “ Ichthyosaurus ” atavus as a species of Mixosaurus . Maisch and Matzke (1998) noted distinct differences in the dentition between Mixosaurus cornalianus and “ Ichthyosaurus ” atavus and proposed a new genus Contectopalatus for the reception of the latter. Motani (1999 b) and various recent authors have treated Contectopalatus as a subjective junior synonym of Mixosaurus . We follow Jiang et al. (2016) in referring “ Ichthyosaurus ” atavus to Phalarodon . Liu et al. (2013) described a nearly complete skeleton including the skull from the Middle Triassic (Anisian) upper Member of the Guanling Formation of Yunnan ( China) and referred it to Phalarodon atavus .

References.

Quenstedt (1851–1852), F. Huene (1916), Edinger (1935), Maisch and Matzke (1998, 2001), Motani (1999 b), Jiang et al. (2006), Liu et al. (2013).

Figures

Figure 9. Reptiles from the Muschelkalk Group. A. Pistosaurid eosauropterygian Pistosaurus longaevus (UMO BT 000015.00), incomplete cranium in oblique lateral view. Scale bar: 2 cm. Photograph courtesy of S. Evers (UMO BT). B. Mixosaurid ichthyosaurian Phalarodon atavus (MB. R. 2353), incomplete cranium in lateral view. Scale bar: 2 cm. Courtesy of N. Fröbisch. C, D. Blezingeria ichthyospondyla (SMNS 81198), dorsal vertebra in (C) anterior and (D) posterior view. Scale bar: 2 cm.