Recovering missing data: estimating position and size of caudal vertebrae in Staurikosaurus pricei Colbert, 1970

Orlando N Grillo,Sergio A.K Azevedo

doi:10.1590/s0001-37652011005000003

Abstract

Missing data is a common problem in paleontology. It makes it difficult to reconstruct extinct taxa accurately and restrains the inclusion of some taxa on comparative and biomechanical studies. Particularly, estimating the position of vertebrae on incomplete series is often non-empirical and does not allow precise estimation of missing parts. In this work we present a method for calculating the position of preserved middle sequences of caudal vertebrae in the saurischian dinosaur Staurikosaurus pricei, based on the length and height of preserved anterior and posterior caudal vertebral centra. Regression equations were used to estimate these dimensions for middle vertebrae and, consequently, to assess the position of the preserved middle sequences. It also allowed estimating these dimensions for non-preserved vertebrae. Results indicate that the preserved caudal vertebrae of Staurikosaurus may correspond to positions 1-3, 5, 7, 14-19/15-20, 24-25/25-26, and 29-47, and that at least 25 vertebrae had transverse processes. Total length of the tail was estimated in 134 cm and total body length was 220-225 cm.

Highlights

Missing data is a major problem in the reconstruction of extinct taxa (Paul 1987, 1988, Czerkas 1997) and has several implications in phylogenetic analyses (Nixon and Davis 1991, Novacek 1992, Maddison 1993, Anderson 2001, Kearney and Clark 2003, Norell and Wheeler 2003) and on biomechanical studies (Holliday et al 2010)
The positioning of vertebrae in an incomplete series is often accomplished by the analysis of the general morphology and size of each fossilized vertebra
The results obtained from the regressions in this work allowed an accurate positioning of the caudal vertebrae in Staurikosaurus price

Summary

Introduction

Missing data is a major problem in the reconstruction of extinct taxa (Paul 1987, 1988, Czerkas 1997) and has several implications in phylogenetic analyses (Nixon and Davis 1991, Novacek 1992, Maddison 1993, Anderson 2001, Kearney and Clark 2003, Norell and Wheeler 2003) and on biomechanical studies (Holliday et al 2010). GRILLO and SERGIO A.K. AZEVEDO muscles are necessary to determine body mass, position of the center of mass and to estimate muscle lengths and volumes (Gunga et al 2007, Hutchinson et al 2007). Gatesy (1990) proposed that the length of the muscle caudofemoralis longus is related to the number of caudal vertebrae that possess transverse processes. To estimate the size of this muscle in fossil taxa that have not preserved a complete series of caudal vertebrae, it is necessary to correctly estimate the position of the preserved caudal vertebrae and, to estimate the dimension of the missing ones, especially of those that have transverse processes

Methods

Results

Conclusion