Timing of cranial suture closure in placental mammals: Phylogenetic patterns, intraspecific variation, and comparison with marsupials

Abstract

Used as markers of postnatal growth closure sequences of 22 ectocranial sutures and synchondroses were recorded in a sample of 1161 skulls belonging to 38 species from all major placental clades: Afrotheria, Xenarthra, Laurasiatheria and Euarchontoglires (Boreoeutheria). The maximum closure level, which is not significantly correlated to body mass, is higher in Afrotheria and Xenarthra than in Boreoeutheria. Only the basioccipito-basisphenoid and the basioccipito-exoccipital synchondroses close in all species sampled, the supraoccipito-exoccipital and the inter-parietal sutures do in most species. Parsimov retrieved more heterochronic shifts for Afrotheria and Xenarthra than for Boreoeutheria. The amount of intraspecific variation differs among the species sampled being high among xenarthran species and low among afrotherians. Specimens (162) representing 12 marsupial genera were also analysed. Placentals exhibit a larger number of suture closures than marsupials and in both groups the sutures at the base of the skull are the first to fuse starting with the basioccipito-exoccipital. ABSTRACT Used as markers of postnatal growth closure sequences of 22 ectocranial sutures and synchondroses were recorded in a sample of 1161 skulls belonging to 38 species from all major placental clades: Afrotheria, Xenarthra, Laurasiatheria and Euarchontoglires (Boreoeutheria). The maximum closure level, which is not significantly correlated to body mass, is higher in Afrotheria and Xenarthra than in Boreoeutheria. Only the basioccipito-basisphenoid and the basioccipito-exoccipital synchondroses close in all species sampled, the supraoccipito-exoccipital and the inter-parietal sutures do in most species. Parsimov retrieved more heterochronic shifts for Afrotheria and Xenarthra than for Boreoeutheria. The amount of intraspecific variation differs among the species sampled being high among xenarthran species and low among afrotherians. Specimens (162) representing 12 marsupial genera were also analysed. Placentals exhibit a larger number of suture closures than marsupials and in both groups the sutures at the base of the skull are the first to fuse starting with the basioccipitoexoccipital. J. Morphol. 275:125-140, 2014.Wiley Periodicals, Inc.

New toxodontid (Notoungulata) from the Early Miocene of Mendoza, Argentina

“…Similar to other toxodontids, the skull is narrow and tall. Several sutures are fused, including some in the facial region of the skull (e.g., lacrimal-frontal, jugal-maxilla), which usually remain open in late ontogenetic stages of other placentals (Krogman 1930;Rager et al 2014). Consequently, MHNSR-PV 1004 can be considered a late adult or senile specimen.…”

Deciduous dentition and dental eruption of Hyainailouroidea (Hyaenodonta, “Creodonta,” Placentalia, Mammalia)

“…The replacement of deciduous teeth, eruption of adult dentition, and subsequent wear contribute information on the rate of maturation across lineages (e.g., Slaughter et al, 1974, Smith, 2000Asher and Lehmann, 2008;Ciancio et al, 2012;Veitschegger and Sánchez-Villagra, 2016). Dental eruption sequences can be compared with other proxies for developmental maturity, such as long bone epiphyseal fusion (Coutinho et al, 1993;Uhen, 2000) and cranial suture fusion (Sánchez-Villagra, 2010b;Rager et al, 2013), to identify key developmental phases in extinct taxa that can be used to reconstruct life histories and phylogenetic relationships (Fink, 1982;Smith, 1989;O'Leary et al, 2013).…”

Supplemental Material for 'Exceptional skull of Huayqueriana (Mammalia, Litopterna, Macraucheniidae) from the late Miocene of Argentina : anatomy, systematics, and paleobiological implications. (Bulletin of the American Museum of Natural History, no. 404)'

“…8B). The nasofrontal suture may obliterate very early in ontogeny, as in elephants, in which it fuses sooner than the basioccipital-basisphenoid synchondrosis (e.g., Loxodonta africana) or immediately thereafter (e.g., Elephas maximus) (Rager et al, 2014).…”