Lisowicia, Sulej & Niedźwiedzki, 2019

Sulej, Tomasz, 2024, Osteology and relationships of the Late Triassic giant dicynodont Lisowicia, Zoological Journal of the Linnean Society 202 (1), pp. 1-56 : 38-40

Lisowicia mode of life

Traditionally dicynodonts are depicted with abducted (directed to outside) forelimbs and nearly adducted (oriented towards the body axis) hindlimbs (Fröbisch 2006, Ray 2006). However, the trackways of a large dicynodont from the Middle Triassic named Pentaoauropuo argentinae make such posture questionable (Hunt et al.1993, Lagnaoui et al. 2019). This track is believed to have been left by a kannemeyerid dicynodont that was a sprawling limbed trackmaker with an abducted posture for the forelimbs and at least a semi-abducted posture for the hindlimbs (Abdelouahed et al. 2019). Sulej and Niedźwiedzki (2019) proposed that the giant Lioosicia bojani had also adducted its forelimbs. This has also been discussed for pelycosaur tracks, which have a much more narrow gauge than the skeleton would seem to indicate. Twisting of the body and/or limbs while walking might explain how this happens (Hunt and Lucas 1998, Hopson 2015).

The analysis of sediments (or bones) from Lisowice shows that Lioosicia lived in an environment near rivers with a lot of oxbow lakes (Dzik et al. 2008). Also, the similarities of coprolites of Lioosicia to Hippopotamuo amphibiuo Linnaeus, 1758 suggest its affiliation with such an environment (Bajdek et al. 2014, 2019). In the case of Placeriao, its bone microstructure suggests even an aquatic style of life (Fiorillo et al. 2000). If they lived in or close to the swamp, they probably could use the soft plants as a food (Bajdek et al. 2014), abundant in such environments. Such an interpretation is not in conflict with the architecture of their skulls.

There is little doubt that all the Triassic dicynodonts were herbivorous, but there are various views on the method by which they collected the food (see: Surkov and Benton 2004). According toCruickshank (1978), Dinodontooauruo, Stahleckeria poteno, Dolichuranuo Keyser, 1973 , Tetragoniao, Rhinodicynodon, Zambiaoauruo , Sinokannemeyeria , and Vinceria Bonaparte, 1969 were browsers, whereas Placeriao, Jachaleria, Iochigualaotia jenoeni, Kannemeyeria , Uralokannemeyeria Danilov, 1971 , Rabidooauruo, Rhadiodromuo, and Wadiaoauruo indicuo were grazers (in the meaning that they ate low-growing plants). Originally, Cox (1965) made this distinction based mainly on the shape of the snout and the orientation of the occipital region of the skull. Ordoñez et al. (2019), based on principal component analyses (PCA) of skulls from South America, showed that the adaptation of Stahleckeria poteno , I. jenoeni, and J. candelarienoio to feeding on the vegetation was characteristic of an arid climate, although the palaeoclimate was seasonal semi-arid when they lived ( Mancuso et al. 2021). The new material from Poland calls for reconsideration of this question.

Most authors discussing the dicynodonts mode of life have focused on their sexual dimorphism ( Owen 1876, Camp and Welles 1956, Barry 1957, Cruickshank 1967, Cox 1969, Bandyopadhyay 1988, Sullivan et al. 2003). The differences between males and females were proposed to be expressed mainly in the presence of the tusks or maxillary horns in males. The lack of conclusive material excludes Lioosicia bojani from these inquires. Most authors agree that the canine tusks or elongated maxillary processes were used in food gathering and fighting (Camp and Welles 1956, Rowe 1979, Bandyopadhyay 1988). Many authors have discussed the mode of feeding of dicynodonts (Cox 1969, Cruickshank 1978, Walter 1985, Hotton 1986), summarized by Defauw (1989), who recognized five dicynodont feeding types: invertebrate collecting specialists, grubbers, browsers, forest litter foragers, and flexible foragers. The functional morphology of the dicynodont masticatory apparatus was studied by Crompton and Hotton (1967), King et al. (1989), Cox (1998), Jasinoski et al. (2009, 2010), and Ordoñez et al. (2019).

Niedźwiedzki et al. (2011, 2012) showed that the archosauriform Smok saseloki Niedźwiedzki et al., 2012 was feeding on dicynodonts in the Late Triassic but probably dicynodonts escaped this predation by evolving into giant size, already in the Middle Triassic. The most numerous preserved bones of the skull of Lioosicia bojani and Placeriao ‘ gigao ’ are postorbitals and basisphenoids, unlike the nasals that are very rare in the case of P. ‘ gigao ’ and unknown in L. bojani . This may mean that the snout was a structurally weak portion of the skull that was the first to disarticulate during rotting of the carcass or the dorsal part of the snout was an attractive target for predators, whereas the postorbital was too massive for them.