Panochthus Burmeister, 1866

Panochthus Burmeister, 1866

Panochthus intermedius Lydekker, 1895 Referred material: Two caudal vertebrae, left incomplete hand, left incomplete hind limb, right incomplete foot, 16 sesamoid bones, 34 small plates of osteoderms from dorsal carapace, and 37 isolated osteoderms: PIMUZ A/V 433 ( Figs. 3 View Fig , 7 View Fig ); 15 plates of osteoderms from dorsal carapace and 14 isolated osteoderms: PIMUZ A/V 435.

Comment: A recent study produced the comparative description of Panochthus species from the Pampean Region from the Ensenadan (Zamorano et al., 2021). Te authors support the presence of just three species of Panochthus in this region at this period: Pan. intermedius , Panochthus subintermedius Castellanos, 1937 , and Panochthus cf. Pan. subintermedius (Zamorano, 2012) . While the shape and size of the fingers and toes of PIMUZ A/V 433 are consistent with assignment to the genus (see Schulthess, 1920), the main argument for the determination is supported by the ornamentation of the multiple osteoderms corresponding to numerous polygonal tubercles equal in size on a single osteoderm (Zamorano et al., 2014a, 2021). Tis feature is unique to certain regions of the dorsal carapace of Pan. intermedius and Pan. subintermedius , mentioned above, but also to the two Lujanian species, Pan. tuberculatus and Pan . frenzelianus. Among the two species from Ensenadan, a distinction is difficult with isolated osteoderms because it is made according to the region of the carapace where central figures are found, the antero- and posterodorsal regions for Pan. intermedius and only the last row of the posterior margin of the carapace for Pan. subintermedius (Zamorano et al., 2021) . In PIMUZ A/V 433 and PIMUZ A/V 435, many osteoderms show no central figure, which indicates other regions of the dorsal carapace with more hexagonal shapes for the more dorsal part, and more quadrangular shapes for the more lateral part (Zamorano et al., 2021). However, for both specimens some osteoderms exhibit a central figure and none of these seem to belong to the last row of the posterior margin of the carapace, indicating a clear assignment of PIMUZ A/V 433 and PIMUZ A/V 435 to Pan. intermedius (Zamorano et al., 2021) . Because Pan. intermedius is significantly larger than Pan. subintermedius , Pan. tuberculatus , and Pan . frenzelianus (e.g., Zamorano et al., 2014a), another possible distinction is directly dependent on relative osteoderm size. In addition, the tubercles of each osteoderm type, hexagonal or quadrangular, of PIMUZ A/V 433 and PIMUZ A/V 435 are particularly large and appear to be closer to Pan. intermedius than to Pan. subintermedius (Cruz et al., 2011; Zamorano et al., 2014a, b, 2021). Accordingly, I propose to reassign these two specimens to Pan. intermedius .