Shape and size variations in the cranium of elephant-shrews: a morphometric contribution to a phylogenetic debate

Abstract

A geometric morphometric analysis was carried out on the crania of 13 species of elephant-shrews (Macroscelidea), a group of African mammals whose phylogeny is still debated. The material examined consisted of 313 crania and included all the genera of Macroscelididae, the unique family recognized by taxonomists. The results obtained from the analysis of the cranium shape and size, either from dorsal or lateral view, were very similar. The Wrst one appeared more reliable because of the higher number of intersection points Wxed between the cranial sutures. All the cranial features that distinguished the genus Rhynchocyon were a consequence of the extreme enlargement of frontal bones. Instead, within the subfamily Macroscelidinae, the diVerences between genera were based on modiWcation involving other bones, mainly mastoids and nasals, as shown by the deformation grids. A cluster analysis conWrmed the traditional subdivision in two subfamilies (Rhynchocyoninae and Macroscelidinae) but suggested a diVerent relationship among the recognized genera belonging to Macroscelidinae. Our results are congruent with data obtained from previous biochemical research and support the traditional subdivision in two subfamilies, the monophily of the genus Elephantulus and its closeness with Petrodromus, relating to their similar cranium shapes. The latter presumably is a case of gigantism as adaptation to forest habitats. Further studies on all the species of Elephantulus could provide new evidence for assessing the relationships within this clade, including Macroscelides that by the present analysis appeared as a well-distinguished taxonomic entity.

Skull size and shape variation versus molecular phylogeny: a case study of alpine newts (Mesotriton alpestris, Salamandridae) from the Balkan Peninsula

“…A phylogenetic signal was inconsistently detected in the mammal skull shape. For example, concordance was found between skull shape variation and phylogeny of rodents (Nicola et al 2003), marmots (Caumul and Polly 2005) and elephant shrews (Panchetti et al 2008). Also, a phylogenetic signal was detected for molar shape in shrews, marmots and mice (Polly 2001(Polly , 2003Macholán 2006), whilst no congruence between morphology and phylogeny was found for the mandible shape in rodents (Nicola et al 2003;Monteiro and Dos Reis 2005).…”

Petrosaltator gen. nov., a new genus replacement for the North African sengi Elephantulus rozeti (Macroscelidea; Macroscelididae)

“…The remarkable and unexpected genetic relationship shared by E. rozeti and Petrodromus is supported by several relatively cryptic morphological characters, including penis morphology (Woodall 1995a), occurrence of male nipples (Olbricht & Stanley 2009), skull morphology (Panchetti et al 2008;Scalici & Panchetti 2011), and innerear structure (Benoit et al 2013). Additionally, Smit et al (2011) presented chromosomal data that support the grouping affinities of these two taxa, with the addition of Macroscelides.…”

Morphological cranial diversity contributes to phylogeny in soft-furred sengis (Afrotheria, Macroscelidea)

“…The underlying goal of our study was to realise the full potential of the application of geometric morphometrics (GM) to describe the variation pattern of the cranium within Macroscelidinae. This study extends the investigation of Panchetti et al (2008) through further analysis of the cranial ventral side rather than the lateral and dorsal surfaces. There is general agreement on the use of the ventral surface of the skull as it is more appropriate than the lateral or dorsal sides for two-dimensional GM analyses.…”

“…Such phylogenetic shuffling led the authors to assume a diphyletic origin for the genus Elephantulus. Indeed, there remains a lack of agreement concerning the phylogeny, in spite of different morphological (Corbet and Hanks, 1968;Corbet, 1995;Panchetti et al, 2008;Olbricht and Stanley, 2009), chromosomal (Tolliver et al, 1989), biochemical (Raman and Perrin, 1997), and biomolecular (Douady et al, 2003;Smit et al, 2008) approaches performed to clarify the within-order relationships.…”