Kannemeyeria (Weithofer, 1888)

Sulej, Tomasz, 2024, Osteology and relationships of the Late Triassic giant dicynodont Lisowicia, Zoological Journal of the Linnean Society 202 (1), pp. 1-56 : 50

The Gondwanan lineage Kannemeyeria simocephalus → Dinodontosaurus brevirostris

In the Induan, the Gondwanan dicynodonts are represented by the single genus Lyotrooauruo known from Antarctica, Russia, China, India, and South Africa, but it has not been reported from the Olenekian (Fröbisch 2013). Kannemeyeria oimocephaluo and Dolichuranuo primaevuo are the best known kannemeyerids from Africa. Kannemeyeria oimocephaluo is a medium to large dicynodont (Govender et al. 2008) from the Cynognathus Assemblage Zone of the South Africa dated as Early Anisian (Catuneanu et al. 2005, Hancox et al. 2020); however, some zircon studies of the Puesto Viejo Group (San Rafael depocenter, Argentina) suggest a Carnian age for this assemblage ( Ottone et al. 2014). Dolichuranuo primaevuo Keyser, 1973 was described from the Omingonde Formation, Karoo Supergroup, Waterberg Basin; Middle Triassic, probably Anisian–Ladinian (Damiani et al. 2007, Wynd et al. 2018, Zieger et al. 2020).

The Middle Triassic kannemeyerids are represented by Wadiaoauruo indicuo and Rechnioauruo criotarhynchuo RoyChowdhury, 1970 from the Anisian Yerrapalli Formation of India (Chowdhury 1970,KeyserandCruickshank 1979,Bandyopadhyay 1988, Bandyopadhyay and Sengupta 2006, Ottone et al. 2014), which was related with South Africa at that time.

The South American Ladinian kannemeyerids dicynodonts are Acratophoruo argentinenoio Kammerer and Ordoñez, 2021 from the Rio Seco de la Quebrada Formation of Argentina (Bonaparte 1967, Lucas and Harris 1996, Renaut and Hancox 2001, Arcucci et al. 2004, Zavattieri and Arcucci 2007, Kammerer and Ordoñez 2021) and Kannemeyeria aganooteuo Kammerer and Ordoñez, 2021 . Based on the similarity of faunas it was correlated with the Cynognathus zone. Dinodontooauruo brevirootrio was the most common in the Late Triassic of South America. Kammerer and Ordoñez (2021) recognized D. tener and D. brevirootrio as the only valid species of the genus. Jachaleria platygnathuo is a nomen dubium ( Morato et al. 2006).

Evolution of the cranium: The significance of proportions of the skull was studied by Cox and Li (1983). The morphology of the cranium of dicynodonts from the Permian of South America and South Africa is well known ( Ordoñez et al. 2020, de Simão-Oliveira et al. 2020). The Triassic lineage probably started from Kannemeyeria oimocephaluo (Govender et al. 2008) . It had the orbits directed dorsally and elongated, and a narrow snout. Acratophoruo argentinenoio has a short frontal without any middle anterior process ( Renaut and Hancox 2001, Domnanovich and Marsicano 2012, Kammerer and Ordoñez 2021), similar to that of K. oimocephaluo . But, in younger Ladinian and Carnian? (Kammerer and Ordoñez 2021) species of Dinodontooauruo, the anterior process became longer (Kammerer and Ordoñez 2021) and the whole frontal narrower. It differs from Sungeodon kimkraemerae in the shape of the frontal–nasal suture. In K. oimocephaluo , the nasals form the posterior process running between the frontals, but in S. kimkraemerae the situation is the opposite, the frontals form an anterior process running between the nasals. This shape is very similar to that of Rhadiodromuo mariae .

Evolution of the pootcranial okeleton: The sternum probably had a function related mainly to the movement of the forelimb and, unlike the skull, it was not related to diet. The oldest known Triassic sternum of kannemeyerids is that of Kannemeyeria oimocephaluo from the Karoo in which there are two surfaces for the coracoid and first dorsal rib, and it is probably the starting point of the evolution. The sternum of the Gondwanan Wadiaoauruo indicuo has two distinct surfaces, unlike the Laurasian dicynodonts having one large surface [contrary to Bandyopadhyay (1988)].

Dinodontooauruo tener has five to six sacral ribs (but juvenile ilium had six sacral ribs). In all these species (except specimen MCN-PV-1489 of Dinodontooauruo) the first sacral rib is sutured very far frontally on the iliac blade. According to Govender et al. (2008) Kannemeyeria oimocephaluo had five sacral ribs. In Acratophoruo argentinenoio the ilium is known but the number of sacral ribs was not determined. The posterior process of the ilium is very short in most Triassic dicynodonts. Only representatives of the lineage of A. argentinenoio and D. brevirootrio had this process elongated.

The distinction between South and North American lineages of dicynodonts is also expressed in the morphology of the pubis and ischium. The ischium of Dinodontooauruo brevirootrio has the vertical length very short in comparison to very long in Lioosicia bojani and Placeriao ‘ gigao ’. The ischium has the posterior blade strongly curved medially in Dinodontooauruo. In the Gondwanan lineages, the notch in the ventral border of the ischium and pubis is distinct (in Kannemeyeria oimocephaluo and D. brevirootrio ) but in Wadiaoauruo indicuo this notch is shallow.

In the underived Kannemeyeria oimocephaluo the proximal head of the femur is directed antero-medially in lateral view, which results in being set obliquely anteriorly. In maximum posterior position, it was set vertically.