Growth in fossil and extant deer and implications for body size and life history evolution

Abstract

BackgroundBody size variation within clades of mammals is widespread, but the developmental and life-history mechanisms by which this variation is achieved are poorly understood, especially in extinct forms. An illustrative case study is that of the dwarfed morphotypes of Candiacervus from the Pleistocene of Crete versus the giant deer Megaloceros giganteus, both in a clade together with Dama dama among extant species. Histological analyses of long bones and teeth in a phylogenetic context have been shown to provide reliable estimates of growth and life history patterns in extant and extinct mammals.ResultsSimilarity of bone tissue types across the eight species examined indicates a comparable mode of growth in deer, with long bones mainly possessing primary plexiform fibrolamellar bone. Low absolute growth rates characterize dwarf Candiacervus sp. II and C. ropalophorus compared to Megaloceros giganteus displaying high rates, whereas Dama dama is characterized by intermediate to low growth rates. The lowest recorded rates are those of the Miocene small stem cervid Procervulus praelucidus. Skeletal maturity estimates indicate late attainment in sampled Candiacervus and Procervulus praelucidus. Tooth cementum analysis of first molars of two senile Megaloceros giganteus specimens revealed ages of 16 and 19 years whereas two old dwarf Candiacervus specimens gave ages of 12 and 18 years.ConclusionsThere is a rich histological record of growth across deer species recorded in long bones and teeth, which can be used to understand ontogenetic patterns within species and phylogenetic ones across species. Growth rates sensu Sander & Tückmantel plotted against the anteroposterior bone diameter as a proxy for body mass indicate three groups: one with high growth rates including Megaloceros, Cervus, Alces, and Dama; an intermediate group with Capreolus and Muntiacus; and a group showing low growth rates, including dwarf Candiacervus and Procervulus. Dwarf Candiacervus, in an allometric context, show an extended lifespan compared to other deer of similar body size such as Mazama which has a maximum longevity of 12 years in the wild. Comparison with other clades of mammals reveals that changes in size and life history in evolution have occurred in parallel, with various modes of skeletal tissue modification.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0295-3) contains supplementary material, which is available to authorized users.

Growth and life history of Middle Miocene deer (Mammalia, Cervidae) based on bone histology

“…Thin-sections were prepared following conventional procedure (Chinsamy-Turan, 2005;Kolb et al, 2015a;Padian and Lamm, 2013). The sections were taken as close as possible from the mid-diaphyseal level (see Appendix A for estimation of relative position of each thin-section).…”

“…Our knowledge of the histology of the Cervidae (deer) was recently expanded with a work describing long bone and tooth histology of various taxa (Kolb et al, 2015a). Included in this study was the Miocene Procervulus, an early cervid whose growth rate was found to be especially low.…”

“…This species was recently included in a study of long bone and dental histology concerned with cervids life history evolution in order to estimate skeletal maturity and growth rate (Kolb et al, 2015a). Procervulus distinguished itself in featuring the lowest estimated growth rate of all the cervids sampled in that study.…”

“…The present study examines further "stem-cervid" bone histology in describing that of other Miocene taxa, Dicrocerus elegans and Euprox sp. With their inclusion in the dataset of Kolb et al (2015a), we estimate the ancestral growth rates among cervids, and studied its correlation with body size. The skeletochronology of Dicrocerus suggests a relatively high growth rate for its body size differing from the condition of Procervulus and Euprox, and hence, documenting diversity in the life history traits of Miocene cervids.…”

An exceptionally well-preserved skeleton of Thomashuxleya externa (Mammalia, Notoungulata), from the Eocene of Patagonia, Argentina

“…An outer circumferential layer (OCL) (Ponton et al, 2004) consisting of avascular lamellar bone is present. The OCL indicates that, despite incompletely fused femoral epiphyses, the specimen reached skeletal maturity (Kolb et al, 2015a;Martinez-Maza et al, 2014). A minimum of three lines of arrested growth (LAGs) could be identified within the OCL (Figure 7.3).…”