Cricosaurus albersdoerferi, (SACHS, YOUNG, ABEL & MALLISON, 2021)

Scavezzoni, Isaure, Fischer, Valentin, Johnson, Michela M. & Jouve, Stéphane, 2024, Form and function of the pelvic girdle of Thalattosuchia and Dyrosauridae (Crocodyliformes), Geodiversitas 46 (6), pp. 135-326 : 176-178

CRICOSAURUS ALBERSDOERFERI ( SACHS, YOUNG, ABEL & MALLISON, 2021)

For measurements, see Tables 7-9 .

Ilium

The ilium of Cricosaurus albersdoerferi ( Fig. 20 ) is overall triangular in shape due to a lack of postacetabular process, as that of other metriorhynchoids (e.g. ‘ Metriorhynchus ’ brachyrhynchus NHMUK PV R 4763, ‘ Metriorhynchus ’ brachyrhynchus NHMUK PV R 3804, Suchodus durobrivensis , Thalattosuchus superciliosus , Cricosaurus suevicus , Dakosaurus maximus , Geosaurus giganteus , etc.). In Cricosaurus albersdoerferi , the preacetabular process seems almost as dorsoventrally thick as it is anteroposteriorly long, giving it a short and stout aspect. Yet, it is possible that the preacetabular process has been flattened and thus shows both dorsal and lateral sides at once. Similar to Cricosaurus suevicus , ‘ Metriorhynchus ’ brachyrhynchus NHMUK PV R 4763, ‘ Metriorhynchus ’ brachyrhynchus NHMUK PV R 3804, Suchodus durobrivensis , Thalattosuchus superciliosus (NHMUK PV R 2054 and NMI F21731), or Geosaurus giganteus , Tyrannoneustes lythrodectikos , the preacetabular process of Cricosaurus albersdoerferi appears in line with the dorsal margin of the bone. Moreover, the preacetabular process of Cricosaurus albersdoerferi seems almost parallel to the ventral margin of the pubic peduncle, as in Suchodus durobrivensis or Geosaurus giganteus .

The anterior margin of the ilium of Cricosaurus albersdoerferi is slightly undulating underneath the preacetabular process: at about its mid height, the concavity of the anterior margin switches from concave dorsally to convex ventrally. Presumably, the sinusoidal shape of the bone along the anterior margin is caused by a faint supraacetabular crest as in Dakosaurus maximus and Geosaurus giganteus . The dorsal and posterior margins of the ilium of Cricosaurus albersdoerferi appear to for a smooth convex continuum almost hemispherical. Cricosaurus suevicus also shows a convex posterodorsal border but the shape is less harmonious.

Ischium

The ischium of Cricosaurus albersdoerferi ( Fig. 20 ) shows the presence of a short and thick peduncle bridge, leading to a rounded anterior peduncle. The anteroposterior length of the peduncle bridge and anterior peduncle of Cricosaurus albersdoerferi is lesser than that of the posterior peduncle, unlike Cricosaurus suevicus . The anterior and posterior margins of the ischium of Cricosaurus albersdoerferi appear concave as in Cricosaurus suevicus , Cricosaurus bambergensis , Torvoneustes carpenteri and Dakosaurus maximus , but are not entirely preserved. Still, it seems that the shaft of Cricosaurus albersdoerferi is larger than the posterior peduncle, similar to many other thalattosuchians (e.g. ‘ Metriorhynchus ’ brachyrhynchus NHMUK PV R 3804, Thalattosuchus superciliosus , Cricosaurus suevicus , Torvoneustes carpenteri , Dakosaurus maximus , Geosaurus giganteus , Lemmysuchus obtusidens , Macrospondylus bollensis , etc.).

Pubis

The pubis of Cricosaurus albersdoerferi ( Fig. 20 ) shows a relatively reduced pubic symphysis and a mediolaterally expanded pubic plate similar to other rhacheosaurines (e.g. Cricosaurus suevicus , Cricosaurus bambergensis ). Hence, due to the reduction of the pubic symphysis, the distal margin of the pubic plate of Cricosaurus albersdoerferi is convex throughout. Like in Cricosaurus suevicus , the pubic apron of Cricosaurus albersdoerferi is not symmetrical compared to the shaft of the pubis, and is more expanded on the medial side of the bone. Compared to other Cricosaurus species, Cricosaurus albersdoerferi shows an abrupt and angular widening of the pubis rather than a smooth concave curve.

Figures

FIG. 20. — Pelvic and thoracic girdle elements of Cricosaurus albersdoerferi (Sachs, Young, Abel & Mallison, 2021) (Sachs et al. 2021), BMMS-BK 1-2 (holotype): A, pelvic girdle and hindlimb; B, thoracic girdle and forelimb. Modified from Sachs et al. (2021). Scale bars: 1 cm.