Skull morphometry and vault sutures of Myrmecophaga tridactyla and Tamandua tetradactyla

Camila M De S Hossotani,Helder S E Luna,José Ragusa-Netto

doi:10.1590/1678-4766e2017038

Camila M De S Hossotani, Helder S E Luna + Show 1 more

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https://doi.org/10.1590/1678-4766e2017038

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Abstract

ABSTRACT This study aimed to examine the relationship between skull size and the level of cranial vault suture closure. A total of 50 Myrmecophaga tridactyla Linnaeus, 1758 and 178 Tamandua tetradactyla Linnaeus, 1758 skulls were analyzed in relation to 18 skull dimensions. The skulls were grouped into three levels of suture closure: no sutures closed (level 0), one or all the fallowing sutures closed: interfrontalis, sagitalis and coronalis (level 1) and all sutures closed (level 2). The results indicated that among the 18 variables measured, 17 showed significant differences (p ≤ 0.01) between level 0 and level 1 skulls of T. tetradactyla; as well as between level 0 and level 1, and level 0 and level 2 skulls of M. tridactyla. M. tridactyla level 1 and level 2 had no significant difference among any of the 18 dimensions. The foramen magnum height in both species showed no significant difference (p > 0.05) among any suture categories. In principle, suture closure level and cranial dimensions are related. The specimens with larger cranial dimensions showed greater number of cranial vault sutures closed for both species of anteaters. Tamandua tetradactyla and M. tridactyla specimens with none of the cranial vault suture closed have a foramen magnum height similar to those with cranial vault suture closed.

Highlights

This study aimed to examine the relationship between skull size and the level of cranial vault suture closure
III) between specimens classified as level 0 and level 1: foramen magnum diameter; occipital condyle breadth; cranial height; cranial breadth; orbital length; nasal breadth; posterior zygomatic arch breadth; pterygoids breadth; supraoccipital length; parietal length; inner nostril breadth; nasal length; palatal width; neurocranium length; frontal length; skull length and maxilla length
Based in our results of the foramen magnum height (FH) between specimens classified as level 0, level 1 and level 2 we believe that both M. tridactyla and T. tetradactyla specimens with small skull dimensions, which we consider to be young, present FH sizes similar to those with larger measurements which are possibly older

Summary

Introduction

This study aimed to examine the relationship between skull size and the level of cranial vault suture closure. Foram analisados 50 crânios de Myrmecophaga tridactyla Linnaeus, 1758 e 178 de Tamandua tetradactyla Linnaeus, 1758 em relação a 18 dimensões do crânio. Tamandua tetradactyla Linnaeus, 1758, commonly called the lesser anteater, belongs to Myrmecophagidae and is widespread in South America (Miranda et al, 2014). It is medium-sized with arboreal and terrestrial habits. The end of the snout has no fused structure, called the pre-maxilla, which is absent in M. tridactyla (Miranda, 2012) Both anteater species have the pterygoids expanded and united in the middle, with no interpterygoid vacuity, in which a soft palate is often present (Reiss, 2000). There are some studies on xenarthrans, which used suture closure level as a parameter to estimate age (Naples, 1982; Squarcia et al, 2009), and this has

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