Teeth out of proportion: Smaller horse and cattle breeds have comparatively larger teeth

There are different descriptions of allometric relationships between important components of the mammalian skull. Craniofacial evolutionary allometry describes a pattern of increasing facial cranium in larger skulls. Another body of literature describes disproportionately larger teeth in smaller species or specimens, matching anecdotal observations with dental problems in dwarf breeds whose teeth appear “too large for their skulls.” We test the scaling of tooth row length with body size and skull length in a data set comprising 114 domestic horses (representing 40 breeds) and in another data set of 316 domestic cattle (of >60 breeds). We demonstrate that smaller skulls have a relatively longer tooth row in both horses and cattle; larger specimens have relatively shorter tooth rows. Whereas in horses, larger skulls have a relatively longer diastema, the distance of the mesial maxillary premolar to the premaxilla was proportional to cranium length in cattle. While the reasons for these patterns remain to be detected, they support the hypothesis that tooth size might be less “evolvable,” in terms of time required for changes, than body size. The pattern may affect (i) the selective breeding for dwarf breeds by setting minimum constraints for skull size, as described previously for domestic horses with the same data set; (ii) the susceptibility of small breeds for dental problems; and (iii) differences in chewing efficiency between breeds of different sizes. The findings support the existing concept that scaling of tooth to body size across taxa becomes more isometric the longer these taxa are separated in evolutionary time

Influences of Domestication and Island Evolution on Dental Growth in Sheep

Funder: Department of Zoology, University of CambridgeFunder: Leverhulme Trust; doi: http://dx.doi.org/10.13039/501100000275Abstract: Domestication and island evolution can lead to changes of life history along the slow-fast gradient. Shifts of life history patterns, in turn, are potentially related to alterations of patterns and timing of tooth eruption. Schultz’s rule predicts an earlier eruption of molars relative to premolars as fecundity increases during the domestication process. On the other hand, evolution on a predator-free, resource limited island might lead to a generally slow life history and delayed tooth eruption, as in the Plio-Pleistocene Balearic caprine Myotragus. In this study, we investigate tooth eruption and its relation to life history in a unique sheep population that is an example of both domestication and island evolution: the ancient and feral Soay sheep (Ovis aries) of the St. Kilda archipelago, Scotland. Tooth eruption timing and sequence is investigated in a comparative framework featuring new data on other domestic sheep (O. aries), including European mouflon (O. a. musimon), as well as wild sheep (O. vignei, O. cycloceros, O. arkal, O. orientalis, O. ammon). These data indicate that the order of eruption is similar in wild and domestic sheep, despite the fundamental life history changes that came about with domestication. However, in contrast to other domestic sheep breeds, Soay sheep erupt their teeth at an absolute older age and also tend to grow more slowly, which resembles the evolutionary trend in island-adapted Myotragus. Despite these similarities, Soay sheep do not share the slow life history pattern inferred for Myotragus, highlighting the distinctive nature of tooth eruption in Soay sheep

The effect of body size evolution and ecology on encephalization in cave bears and extant relatives

Abstract Background The evolution of larger brain volumes relative to body size in Mammalia is the subject of an extensive amount of research. Early on palaeontologists were interested in the brain of cave bears, Ursus spelaeus, and described its morphology and size. However, until now, it was not possible to compare the absolute or relative brain size in a phylogenetic context due to the lack of an established phylogeny, comparative material, and phylogenetic comparative methods. In recent years, many tools for comparing traits within phylogenies were developed and the phylogenetic position of cave bears was resolved based on nuclear as well as mtDNA. Results Cave bears exhibit significantly lower encephalization compared to their contemporary relatives and intraspecific brain mass variation remained rather small. Encephalization was correlated with the combined dormancy-diet score. Body size evolution was a main driver in the degree of encephalization in cave bears as it increased in a much higher pace than brain size. In Ursus spelaeus, brain and body size increase over time albeit differently paced. This rate pattern is different in the highest encephalized bear species within the dataset, Ursus malayanus. The brain size in this species increased while body size heavily decreased compared to its ancestral stage. Conclusions Early on in the evolution of cave bears encephalization decreased making it one of the least encephalized bear species compared to extant and extinct members of Ursidae. The results give reason to suspect that as herbivorous animals, cave bears might have exhibited a physiological buffer strategy to survive the strong seasonality of their environment. Thus, brain size was probably affected by the negative trade-off with adipose tissue as well as diet. The decrease of relative brain size in the herbivorous Ursus spelaeus is the result of a considerable increase in body size possibly in combination with environmental conditions forcing them to rest during winters

Life History Evolution in Extant and Extinct Laurasiatheria – Case Studies Elucidating the Junctions among Selective Forces, Disparity,and Trait Evolution

Abstract This thesis presents several case studies on life history evolution in Laurasiatheria, a diverse group of mammals occupying a wide range of habitats. The respective group in each case study was chosen based on its suitability to answer an underlying question. Additionally, one case study investigates domestication as driver for variation within a species. The first case study aims for a closer look on the Schultz’s rule and heterochro -ny in the relative eruption sequence of the permanent dentition in lower jaws of deer, Cervidae. Cervids were chosen because of their relative uniform mandibular architecture. Schultz’s rule implies that slower growing animals replace their deciduous teeth earlier in relative sequence compared to molar eruption to counterbalance tooth decay and maintain a functional tooth set during growth. The study revealed several heterochronic shifts in tooth eruption during the evolution of deer and resulted in an ancestral tooth eruption sequence, which can also be found in the fossil record. In contrast, the relative eruption sequence is not correlated with any life history variable and thus it does not provide in formation about the life history of cervids. The second study investigated the brain size of cave bears and compared it to extant bear species. Encephalization, or brain size in relation to body size, is linked to some life history variables in Ursidae such as gestation time, newborn mass, weaning mass, and litter size. The results suggest that cave bears had a small brain compared to body size, due to a decoupled body and brain size evolution in which the increase of body size outpaced the one of brain size. Additionally, the trade-off between fat storage and brain size as well as diet might have impacted the relative brain size of cave bears. The degree of encephalization of cave bears suggests that this species gave birth to many, light weighted cubs and had prolonged gestation; mass at weaning was small. The growth of different bear species was investigated using histological thin sections of the midshaft of femora. The growth rate of cave bears from different European localities was investigated and compared to the one of black bears, brown bears, polar bears, sloth bears, and sun bears. The bone cortex of all bear species exhibits a fibrolamellar complex and mostly varies in amounts of parallel-fibered and lamellar bone. Cave bears exhibit a high growth rate and late maturity. The altitude of the locality in which the cave bear remains were found was correlated with growth rate. The growth rate of cave bears indicates that this species gave birth to many, small offspring. In the final case study presented in this thesis, the aim was to investigate how domestication affects variation within a species. For this, the extinct Niata cattle from South America was used as case study. The Niata was a heavy brachycephalic cattle variety. It was described by Darwin and sparked debates among scientists in Europe due to its peculiar appearance. These debates are addressed in an integrative investigation of the Niata using anatomical description, geometric morphometrics, finite element analysis, and genetic analysis. The anatomical description shows clear distinctions between the Niata traits and lethal malformations with which its brachycephaly was compared. The morphometric and genetic analyses show the distinctiveness of the Niata compared to other cattle and places it close to the European taurine breeds. Additionally, the finite element analysis revealed released stress on the Niata skull during bilateral bite. The Niata is an illustrative case on how human intervention shapes domesticated species. To summarize, the case studies presented in this thesis exemplify how bones and teeth can be used to infer life history of extant and extinct animals as well as how humans shape animals during domestication. Keywords: heterochrony, Schultz’s rule, encephalization, hibernation, palaeohistology, growth rate, domestication, chondrodysplasi

Additional file 2: Table S2. of The effect of body size evolution and ecology on encephalization in cave bears and extant relatives

Data subset of brain volume estimates based on external measurements by Finarelli [74] and glass bead method. (XLSX 12 kb

Additional file 3: Supplementary Information. of The effect of body size evolution and ecology on encephalization in cave bears and extant relatives

Results for different linear models and corresponding graphical output as well as boxplot on residuals based on PGLS with all species. (PDF 658 kb

MN10 Prolagus (Ochotonidae, Lagomorpha) from Austria: a new tile for the central European palaeobiogeography of the genus

In the framework of the renewed interest for the study of lagomorph taxonomy and palaeobiogeography in Central Europe, we studied the remains attributed to the genus Prolagus in the MN10 of Austria and recognized two species: P. aff. crusafonti (Richardhof-Wald, early MN10) and Prolagus sp. (Schernham, late MN10). Our results suggest that the evolution of the genus Prolagus followed different pathways in eastern Central Europe at least since early Late Miocene and evidences that the palaeobiogeography of Prolagus in European Late Miocene is much more complicated than previously expected

A Late Pleistocene to Holocene succession of leporid species in the southern Vienna Basin (Austria)

The new archaeological and palaeontological site of Smrcka Lorenz-Abris yielded three different leporid species in stratigraphical sequence, mirroring the effect of environmental changes and the influence of humans in this area. Lepus timidus is a species with a wide Late Pleistocene distribution, but disappeared in the Vienna Basin at the end of the Pleistocene. Lepus europaeus appeared in the Holocene and became dominant in lower altitudes in Austria. Interspecific competition as well as anthropogenic and natural environmental changes are the main factors that caused this replacement. At Smrcka Lorenz-Abris, L.europaeus became dominant around 7000 a BP. This site yielded the last evidence of a mountain hare in the Vienna Basin, with a preserved lower jaw that was dated to be from around14,000 a BP. The most recent immigrant is Oryctolagus cuniculus, which was introduced to Austria, and only found in the upper parts of the section