LOCOMOTOR MORPHOTYPES, ALLOMETRY, LINEAR REGRESSIONS AND THE SMALLEST SIzES IN ORNITHISCHIA: ESTIMATING BODY LENGTH USING HIND LIMB VARIABLES

Marcos Gabriel Becerra, Mariano Andres Ramirez

Abstract


The metatarsus of the heterodontosaurid MPEF-PV 3826 is one of the smallest known for Ornithischia, and size estimation based
on this specimen may reveal new frontiers regarding the smallest sizes reached in the lineage. Aiming to estimate the body size of MPEF-PV
3826 and present a conservative model for size estimation in fragmentary fossil specimens, several linear regressions were performed relating
the length of hind limb bones with body length and sampling different species along all major ornithischian lineages. For each case, the
variables were analysed using linear regressions of raw and logarithm-transformed datasets, excluding the obtained outliers and considering
possible gait-related partitions. The best models were chosen based on their adjustment, their predictive capabilities, locomotor morphotypes
and the possibility of hind limb preservation. The best model selected to estimate the body length of MPEF-PV 3826, based on metatarsal-III
length, revealed a 430.68 mm long body, which is amongst the smallest known for Heterodontosauridae. Linear models can represent a useful
tool for body length estimation based on hind limb measurements of fragmentary ornithischian specimens. MPEF-PV 3826, an active component
of the paleocommunity rather than a hatchling individual, is hereby proposed to represent one of the smallest ornithischian
specimens ever known, playing an important role in the understanding of the paleoecology of Early Jurassic faunas.

Keywords


Linear regressions; Estimation; Body length; Ornithischia; Heterodontosauridae

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