Ticinosuchus ferox Krebs, 1965

Nesbitt, Sterling J., 2011, The Early Evolution Of Archosaurs: Relationships And The Origin Of Major Clades, Bulletin of the American Museum of Natural History 2011 (352), pp. 1-292 : 24-26

Ticinosuchus ferox Krebs, 1965 (figs. 9–10)

AGE: Anisian-Ladinian, Middle Triassic ( Rieber, 1973).

OCCURRENCE: ‘‘Grenzbitumen’’ horizon, Monte San Giorgio, Tessin, Switzerland.

HOLOTYPE: PIZ T2817, essentially complete skeleton.

REFERRED MATERIAL: PIZ T2471, six articulated caudal vertebrae with osteoderms; BES 189 at Museo Civico di Storia Naturale, Milano.

REMARKS: Ticinosuchus was named by Krebs (1965) based on an essentially complete skeleton found near the Anisian-Ladinian boundary in marine sediments. The skeleton preserves most elements in either articulated or disarticulated state. However, as noted by Krebs (1965), many of the bones are heavily crushed, hidden by other elements, or have poorly preserved surfaces.

This has prevented comparison of individual elements to other pseudosuchian taxa, and many features cannot be scored into phylogenetic analyses. As a result, the phylogenetic position is poorly supported in the few analyses in which it has been included (e.g., Parrish, 1993; Benton, 2004).

I examined the skull region very carefully and have a few comments. Unfortunately, the blocks with skull elements appear to have been reassembled incorrectly. The skull must have been split longitudinally when collected, and a portion of the right side was placed incorrectly posterior to the left side of the skull (see fig. 9). This is apparent because the specimens from the ‘‘Grenzbitumen’’ horizon were collected in pieces, then reassembled later (Furrer, personal commun.). The medial surface of the right maxilla is exposed laterally, and there is a large gap between the anterior and posterior portions of the skull. Once this incorrectly placed piece is removed and the anterior and posterior portions of the skull are brought back together, the skull becomes much shorter (see fig. 9). Parts of the skull that were not originally identified include the left frontal and postfrontal in ventral view, the left parietal in lateral view, an upside-down left prearticular in medial view, the impression of the left angular, the left nasal in ventral view, and?left lacrimal in?medial view (see fig. 9).

The holotype of Ticinosuchus ferox preserves the remains of its last meal (fig. 10), and this represents one of the few examples of prey choice in any Triassic archosaur (see Nesbitt et al., 2006). A small collection of fish scales is present at the base of the tail posterior to the ilium and the proximal portion of the ischium. The three-dimensional structure consists of a tan matrix with randomly oriented fish scales (fig. 10D–E). Even though there are a few fish scales located throughout the matrix in which Ticinosuchus is entombed, the abundance of fish scales at the base of the tail far exceeds any other concentration on the slab. It is clear that Ticinosuchus included fishes in its diet, and it is unclear to which taxon or taxa the scales belong. Unfortunately, the identity of the fish as either freshwater or marine is not known at this time. The prey choice of Ticinosuchus may explain why the seemingly terrestrial carnivore would be found in marine sediments. It is clear that Ticinosuchus must have been living close to the shoreline. A similar taxon, Qianosuchus , was also found in marine sediments. Therefore, it is possible that Qianosuchus may have also lived near the shoreline.

Krebs (1965) described much of the skeleton of Ticinosuchus in detail; however, Parrish (1993) discussed a few features of the osteoderms. Parrish (1993) stated that Ticinosuchus has only one paramedian pair of osteoderms per vertebral segment. Nevertheless, it is clear from partially articulated segments of osteoderms, the small size of individual osteoderms, and the number of osteoderms preserved that there must be more than one paramedian pair of osteoderms per vertebral segment.

Pinna and Arduini (1978) referred a specimen (BES 189) from the Middle Triassic strata of Besano to Ticinosuchus . The specimen consists of partial forelimbs and pectoral girdle, an osteoderm, a tooth, and part of the mandible. The morphology of the osteoderm is consistent with that of Ticinosuchus , Prestosuchus , and Saurosuchus . The other bones do not bear any unique apomorphies for Ticinosuchus . Therefore, this taxonomic

assignment is not followed. Only PIZ T2817 is scored for Ticinosuchus .

KEY REFERENCES: Krebs, 1963, 1965; Pinna and Arduini, 1978.