Supervisors info:
Γεώργιος Λύρας, Αναπληρωτής Καθηγητής, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών
Summary:
Although the Cretan hippopotamus (Hippopotamus creutzburgi) has been the subject of many studies, many details of its cranial anatomy remain unknown. This is mainly due to the poor preservation of most Cretan hippopotamus’ fossils. The present study aims to estimate the body mass of the Cretan hippopotamus, describe its craniodental anatomy, and study the changes that occur under the influence of dwarfism. Material from the Katharo Plain in eastern Crete is used for this purpose. The Katharo plain is a globally renowned paleontological site due to the presence of H. creutzburgi fossils, with excavation and publication history dating back to the 19th century. The material used in this study comes from the excavations of the National and Kapodistrian University of Athens (Museum of Paleontology and Geology, NKUA) and the excavations of Dorothea Bate (Natural History Museum, London). Specifically, 15 cranial fragments, 9 mandible fragments, 42 isolated teeth, and 54 postcranial bones of H. creutzburgi were studied. Using allometric equations, it was estimated that the body mass of the Cretan hippopotamus was 425 kg. From the study of H. creutzburgi skull samples, it is observed that the palatum is relatively narrow, the dental rows are subparallel, relatively straight but with a slightly sigmoid shape, converging/bending at P4-M1 and M3. The greatest tooth wear is observed on the first molar M1 in all three skull samples. The length of the upper molar series (M1-M3) is shorter than in H. amphibius and H. antiquus but longer than in Choeropsis liberiensis and H. minor. The proximal part of the mandible is narrow, and the symphysis is short. The body of the mandible is low in height, robust, and elongated. The two horizontal branches of the mandible have a subparallel relationship, and the body laterally is relatively vertical and does not show significant outward inclination at the lower part. The relative length of the Cretan hippopotamus's snout is shorter than that predicted by the static allometry of continental H. amphibius. This means that the Cretan hippopotamus has a shorter snout than a continental hippopotamus with the same cranial size. In the length/width diagrams of the molars, the observed fluctuations of the allometric trends indicate that the dwarf H. creutzburgi does not follow the intra-specific allometries of the continental large hippopotamuses H. amphibius and H. antiquus. H. creutzburgi is not an exact miniature of the continental H. amphibius and H. antiquus. In other words, the dwarf species exhibits modified allometry from its ancestor, and while it evolves in size, its morphology also changes through modifications in ontogeny.
Keywords:
Hippopotamus creutzburgi, Pleistocene, Crete, Insular dwarf species, Craniodental anatomy
