Microanatomical diversity of amniote ribs: an exploratory quantitative study

Abstract

Bone microanatomical diversity in extant and extinct tetrapods has been studied extensively, using increasingly sophisticated quantitative methods to assess its ecological, biomechanical and phylogenetic significance. Most studies have been conducted on the appendicular skeleton, and a strong relationship was found between limb bone microanatomy and habitat preferences. Few comparative studies have focused on the microanatomy of the axial skeleton and its ecological signal. In the present study, we propose the first exploratory study of the microanatomical diversity of amniote ribs. Our comparative sample comprises 155 species of extant amniotes and encompasses the taxonomic, ecological, and body size diversity of this group. We standardized our sampling location to the midshaft of mid-dorsal ribs. Transverse sections were obtained from classical petrographic methods, as well as by X-ray microtomography. Most of the microanatomical and size characters of the ribs display a phylogenetic signal, which is an expected result and is also observed in amniote limb bones and vertebrae. We found a significant relationship between rib cortical thickness, global compactness, and lifestyle. As for the vertebrae, the development of the spongiosa in the medullary region appears to be strongly correlated with size. Even though an ecological signal was found in the inner structure of the ribs, additional work is needed to document the intra-individual variability of the rib microanatomy along the rib cage and within a single element.

Preliminary observations on the bone histology of the Middle Triassic pseudosuchian archosaurBatrachotomus kupferzellensisreveal fast growth with laminar fibrolamellar bone tissue

“…The proximal rib sample reveals a reduction in growth rate, indicated by a closer spacing of LAGs after LAG 6. The comparison of the rib of Batrachotomus with several modern taxa (lepidosaurs, archosaurs, and mammals) supports the results of Canoville et al (2016) that rib microstructure is largely related to body size (and to a lesser amount to life style), because Batrachotomus shares with most larger taxa the presence of a spongiosa surrounded by a ring of compact cortex (Canoville et al, 2016).…”

Microstructure of Vertebrae, Ribs, and Gastralia of Triassic Sauropterygians—New Insights into the Microanatomical Processes Involved in Aquatic Adaptations of Marine Reptiles

“…The observed histological variability reflects differences in sampling location along the rib shaft as well as taxonomical differences and different anatomical positions and thus function of the ribs in the trunk region (e.g., presence of fibers). A correlation of the development of the spongiosa in the medullary region with size as Canoville et al () found was not documented for Triassic Sauropterygia.…”

“…Rib microanatomy was in the focus of a few studies (e.g., de Buffrénil and Mazin, ; de Buffrénil et al, ; Amson et al, ;Houssaye et al, ; Canoville et al, ) but comparison is often difficult due to the lack of a homologous sampling location along the ribs and between ribs along the ribcage (Houssaye et al, ). Canoville et al () were the first who provided an overview of rib inner organization conducted on a large sample of extant amniotes from which standardized midshaft sections of middorsal ribs were taken. They found that ribs exhibit an ecological signal.…”

“…Besides gross‐morphological changes affecting the skeleton, the microstructure (i.e., inner structure) of skeletal elements is also affected due to changing requirements in locomotion and buoyancy. Bone microanatomy, that is, the amount and distribution of the osseous tissue in the bone, is strongly associated with lifestyle and bone biomechanics (e.g., Canoville and Laurin, ; Canoville and Laurin, ; Houssaye et al, ; Dumont et al, ; Quémeneur et al, ; Houssaye et al, ; Canoville et al, ) and can thus indicate ecological preferences (e.g., de Buffrénil et al, , de Buffrénil and Mazin, , Laurin et al, , Germain and Laurin, , Laurin et al, , Laurin et al, , Houssaye et al, , Houssaye et al, ). Further on, changes of microanatomical patterns during the evolutionary history of a clade can document processes of secondary aquatic adaptations (e.g., de Buffrénil et al, ; Amson et al, ; Houssaye et al, ).…”

Ecological and phylogenetic variability in the spinalis muscle of snakes

“…Quantifying and categorizing behavioural ecology is difficult, particularly in such broadly defined regimens as habitat (Al-Kahtani et al, 2004;Gartner et al, 2010;Canoville et al, 2016). Like many other animals, snakes rarely reside in exclusively one type of habitat, although notable exceptions include the viviparous sea snakes and blind snakes (Scolecophidia).…”