Lisowicia bojani, 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 : 32-38

Reconstruction of the Lisowicia bojani skeleton

Skull

The reconstruction of the skull of Lioosicia bojani ( Fig. 47 ) is based on bones coming from a few individuals. They represent parts of the skull roof ( ZPAL V. 33/MB/18), braincase ( ZPAL V. 33/531), and single bones (maxilla ZPAL V. 33/85, postorbital ZPAL V. 33/708, parietal ZPAL V. 33/741, stapes) or their fragments from different individuals: the premaxilla, paroccipital.

The general proportion of the skull was taken from the new reconstruction of P. ‘ gigao ’.

Cranium: The relationship of the frontal to postorbital is clearly visible in the specimen ZPAL V. 33/MB/18. A parietal foramen forms a canal the shape of which can be recognized in this specimen and in the whole parietal (specimen ZPAL V. 33/741). The dorsal edge of the frontal and parietal are visible in lateral view, the latter only slightly raised. The positions of the lacrimal and maxilla are based on Jachaleria candelarienoio , R. criotatuo , and P. ‘ gigao ’. The setting of the squamosal was reconstructed according to morphology of this element in P. ‘ gigao ’.

Mandible: The posterior part of the mandible is preserved in two specimens, ZPAL V. 33/735 and ZPAL V. 33/736. They consist of the articular, surangular, and prearticular. The angulars are also preserved, but always as isolated elements. The dentary and splenial are missing. The reconstruction of the posterior part of the mandible is based on general proportions in other Triassic dicynodonts and on the fit with known elements. The shape of the elongated dentary was based on an extremely elongated bone in Woznikella triradiata (length/deep— 16.6 cm × 6.2 cm = 2.67, probably the ancestor of Lioosicia in Europe).

Postcranial skeleton

The limb postures of kannemeyeriid dicynodonts were studied by Walter (1986) and Fröbisch (2006). Most of the material of Middle and Late Triassic dicynodonts consists of disarticulated skeletons or their parts. Rare articulated skeletons represent different groups of Triassic dicynodonts. These are: Shanoiodon sangi Yeh, 1959, Shanoiodon suhoiangenoio Yeh, 1959, Tetragoniao njaliluo von Huene, 1942, and Angonioauruo cruickohanki among Shansiodontini (Cox 1965) and Kannemeyeria oimocephaluo among Kannemeyeriini (Lehman 1961). The most complete are Parakannemeyeria youngi , Xiyukannemeyeria brevirootrio Liu and Li, 2003 , P. xingxianenoio , Sinokannemeyeria yingchiaoenoio, Dinodontooauruo tener , Rhadiodromuo klimovi , and Iochigualaotia jenoeni.

Two species were selected as the reference standard for the reconstruction of the skeleton of Lioosicia bojani : Parakannemeyeria youngi and Sinokannemeyeria yingchiaoenoio .

Their humeri, ulnae, and radii have proportions closely similar to the bones of L. bojani , despite different construction of the forelimb. Other dicynodonts differ substantially from L. bojani , for instance adult Dinodontooauruo tener material from Harvard has a very short scapula in relation to the length of the humerus (Cox 1965: fig. 11).

The vertebral spine of Lioosicia bojani and its relationship to the pelvis was based on the fit of bones in the individual ZPAL V. 33/720. The proportions of the pectoral girdle and forelimb were based on the proportions in the Parakannemeyeria youngi specimen IVPP V. 979; with respect to the length of scapula vs. length of the humerus, it is 1.25, and the length of the humerus vs. length of the ulna is 1.10. The length of the scapula vs. length of the sternum is 1.61 in Sinokannemeyeria yingchiaoenoio specimen IVPP V. 974. The length of the ulna vs. length of the radius is 1.88 in S. yingchiaoenoio specimen IVPP V. 974 (measurements from: Sun 1963).

Pelvic girdle and forelimb: The position of the humerus and scapulocoracoid in Lioosicia bojani is similar to that in large mammals, such as rhinoceroses and hippopotami, as well as quadrupedal dinosaurs, such as the ceratopsians (Sulej and Niedźwiedzki 2019). In most Triassic dicynodonts the scapula was s et al most vertical and humerus almost horizontal. Such articulation would be difficult to maintain by an animal of L. bojani size. Also, the trackway of some dicynodont shows the manus and pes in the same line (Hunt et al. 1993) and thus contradicts the traditional reconstruction of their forelimb. The disposition proposed for Triceratopo horriduo Marsh 1889 (Fujiwara 2009) with a more horizontal scapula and vertical humerus (very similar to L. bojani ) seems more realistic. The size of the joint for the scapula on the posterior side of the humerus corresponds to the position of this bone. Large Stahleckeria poteno that had area of the articulation with the scapula small probably represents an intermediate stage between the horizontal humerus of small dicynodonts with a small joint for the scapula (for instance Oudenodon bainii Kammerer et al., 2011 (earlier Dicynodon halli ) and Placeriao ‘ gigao ’ that had an already large posterior joint for the scapula. An advanced stage with the vertical position of the humerus is represented by L. bojani , which has a non-rotating humerus with a very large joint for the scapula.

The shift of the humerus to a vertical position should be related to some changes in its articulation with the ulna and radius. The published illustrations of the dicynodont radii are too superficial to enable comparison with that of Lioosicia bojani . This makes the well-preserved proximal part of the quite well-preserved radius from New Mexico NMMNH P-13002 important. This bone and associated femur, part of scapula and axis were described as Iochigualaotia jenoeni? by Lucas and Hunt (1993) but Kammerer et al. (2013) assigned it to Stahleckeriidae indet. based on the shape of the femur.

The scapula NMMNH P-13003 is a distal part of the bone showing the scapular spine and acromion process (nomenclature from: Vickaryous and Hall 2006). It seems that the scapula was very similar to that of Placeriao ‘ gigao ’. The radius has a well-visible head bent outward, which is distinct also in Iochigualaotia jenoeni, Jachaleria candelarienoio , and Lioosicia bojani (all with not preserved clavicles and a small acromion process) and not known in other dicynodonts [illustration of Prioterodon mackayi Huxley, 1868 earlier Diaelurodon shaitoi in Watson (1917: fig. 13) suggests that it was present in this species]. But the bending has a different position in the radius from New Mexico then in I. jenoeni, J. candelarienoio , and L. bojani . In these dicynodonts it is situated in the posterior part of the head, whereas in the New Mexico specimen it is in an anterior position, like D. shaitoi , which had a horizontal position of the humerus.

Thearticulationofthecoracoidandanteriorpartofthesternum occurs in the Struthio cameluo Linnaeus, 1758 , Diplodocuo Marsh, 1878 (Hohn et al. 2011), Alligator Cuvier, 1807 , Tachyglooouo Illiger, 1811, and Ornithorynchuo Blumenbach, 1800 (Gregory and Camp 1918). In Lioosicia bojani, the coracoid has a large joint with the anterior part of the sternum. In the coracoid of Placeriao ‘ gigao ’ UCMP 32449, the area for attachment with the sternum is clearly visible.

Sternum: The latest Triassic Lioosicia bojani has an articulation area on the sternum in its posterior part. The sternum of the Anisian ( Liu et al. 2017) Sinokannemeyeria yingchiaoenoio has an articulation for the coracoid and first dorsal rib in the middle of its length. Cox (1965), based on the specimen MCZ 3120, depicted the sternum of Iochigualaotia jenoeni with an articulation area in its posterior part. It is the only specimen in the Harvard collection with all bones of the pectoral girdle articulated, although not all are in anatomical positions. The problem with the sternum is that it is strongly compressed, and no articulation surface is visible. The Cox (1965) interpretation was based only on the general shape of the bone.

Romer (1956) showed the sternum of Kannemeyeria oimocephaluo posterior to the scapulocoracoid. In the skeleton reconstruction of Dinodontooauruo brevirootrio at Harvard, the interclavicle is at the level of the procoracoid, and the sternum is more posterior than in the specimen MCZ 3120. In such a probably correct position, the articulation area on the sternum can contact the posterior process of the coracoid (Sulej and Niedźwiedzki 2019).

Clavicle: An intriguing problem is the presence of the clavicle and interclavicle in Lioosicia bojani . It was hypothesized by Sulej and Niedźwiedzki (2019: fig. 1), but the very small acromion process on the scapula, which in other dicynodonts was much larger and designed for articulation with the clavicle, contradicts its presence ( Fig. 48 ). On the other hand, the anterior lower part of the scapula in L. bojani is much larger and the sternum is much higher than in most dicynodonts. This difference suggests different functioning of the whole girdle. Sulej and Niedźwiedzki (2019) showed that L. bojani had erect forelimbs, unlike all other dicynodonts. Instead of them, Triceratopo or the rhinoceros may serve as the analogues for the construction of the shoulder girdle. They do not have clavicles because of the erect position of the forelimb. Probably a similar situation was in L. bojani . The loose connection of the olecranon process with the main body of the ulna in its skeleton is probably related with the position of the forelimb. In most large dicynodonts the olecranon is fused with the ulna (Wadiaoauruo, Stahleckeria , Jachaleria , and Sinokannemeyeria ), and that was related to a sprawling posture. The m. triceps attached to the olecranon process, the humerus, and the scapula was among the muscles responsible for keeping the animal in that position. When the humerus was rotated posteriorly to support the erect posture, other muscles became responsible for it. Among them were m. pectoralis, m. supracoracoideus (with a much larger area for articulation on the scapula than in other dicynodonts) and m. coracobrachialis (Sulej and Niedźwiedzki 2019). The loose olecranon process is known also in Placeriao ‘ gigao ’ (Camp and Welles 1956), but in this species the acromion was of the standard shape and it remains unknown how the rotation of the humerus took place.

Presumably Placeriao represents an early stage of the evolution towards the erect posture.

Figures

Fig. 47. Lioosicia bojani Sulej and Niedźwiedzki, 2019 from Lisowice-Lipie Śląskie. Reconstruction of skull (A, B) and mandible (C) based on many elements described in text, in lateral (A, C), and dorsal (B) views.

Fig. 48. Lioosicia bojani Sulej and Niedźwiedzki, 2019 from Lisowice-Lipie Śląskie. A, reconstruction of skeleton in lateral view. Ŋe proportions from Parakannemeyeria chengi, and the shape of the manus and foot are based on Camp and Welles (1956). B, reconstruction of vertebral column in lateral view.