Evidence for prey preference partitioning in the middle Eocene high-diversity crocodylian assemblage of the Geiseltal-Fossillagerstätte, Germany utilizing skull shape analysis
2017
The Geiseltal fossil collection from southern Sachsen-Anhalt Germany contains remarkably
well-preserved fossils of middle Eocene age. These include several crocodylian skulls,
representing at least four different genera with a fifth genus represented by two
mandibular rami. As sites with this many crocodylian genera are unknown in modern
ecosystems, it has been hypothesized that these crocodylians may have differences in habit
as compared to living crocodylians. In order to test similarities between the Geiseltal
crocodylians and extant species, an analysis was conducted using geometric morphometrics
to quantify shape in crocodylian skulls of all living species ( n = 218)
and all well-preserved crocodylian skulls of the Geiseltal fauna ( n =
28). A relative warps analysis was used to quantify and compare skull shape, revealing
Allognathosuchus and Boverisuchus to be very distinct
from each other as well as from Asiatosuchus and
Diplocynodon . Overlap in shape alone exists between some
Diplocynodon and some Asiatosuchus , but there was
significant difference in adult size. When compared with extant crocodylians, three
Geiseltal genera occupied distinctly non-modern morphospace in the first two relative
warps axes. Comparison of the diets of living crocodylians with similarly shaped skulls
was used to reconstruct the prey preferences of the Geiseltal crocodylians, revealing
differences in specialization. During the middle Eocene high global temperatures,
partitioning of prey preference may have allowed this group to attain its higher than
usual diversity, reducing the amount of direct competition.
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