A morphometric analysis of the forelimb in the genus Tapirus (Perissodactyla: Tapiridae) reveals influences of habitat, phylogeny and size through time and across geographical space

Maclaren, James; Hulbert, Richard C.; Wallace, Steven C.; Nauwelaerts, Sandra

doi:10.1093/zoolinnean/zly019

Cited by 20 publications

(26 citation statements)

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“…This is coherent with previous results obtained on cranial shape data indicating a marked correlation between body mass and centroid size (both of the skull and mandible) for many mammalian lineages, especially modern rhinos (Cassini, Vizcaíno & Bargo, 2012). Another study focusing on tapirs tend to highlight a good correlation between centroid size and body mass estimation when using the forelimb elements (MacLaren et al, 2018).…”

Section: Discussionmentioning

confidence: 99%

Interspecific variation in the limb long bones among modern rhinoceroses—extent and drivers

Mallet

Cornette

Billet

et al. 2019

PeerJ

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Among amniotes, numerous lineages are subject to an evolutionary trend toward body mass and size increases. Large terrestrial species may face important constraints linked to weight bearing, and the limb segments are particularly affected by such constraints due to their role in body support and locomotion. Such groups showing important limb modifications related to high body mass have been called “graviportal.” Often considered graviportal, rhinoceroses are among the heaviest terrestrial mammals and are thus of particular interest to understand the limb modifications related to body mass and size increase. Here, we present a morphofunctional study of the shape variation of the limb long bones among the five living rhinos to understand how the shape may vary between these species in relation with body size, body mass and phylogeny. We used three dimensional geometric morphometrics and comparative analyses to quantify the shape variation. Our results indicate that the five species display important morphological differences depending on the considered bones. The humerus and the femur exhibit noticeable interspecific differences between African and Asiatic rhinos, associated with a significant effect of body mass. The radius and ulna are more strongly correlated with body mass. While the tibia exhibits shape variation both linked with phylogeny and body mass, the fibula displays the greatest intraspecific variation. We highlight three distinct morphotypes of bone shape, which appear in accordance with the phylogeny. The influence of body mass also appears unequally expressed on the different bones. Body mass increase among the five extant species is marked by an increase of the general robustness, more pronounced attachments for muscles and a development of medial parts of the bones. Our study underlines that the morphological features linked to body mass increase are not similar between rhinos and other heavy mammals such as elephants and hippos, suggesting that the weight bearing constraint can lead to different morphological responses.

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Section: Discussionmentioning

confidence: 99%

Interspecific variation in the limb long bones among modern rhinoceroses—extent and drivers

Mallet

Cornette

Billet

et al. 2019

PeerJ

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“…Morphological comparisons of the forelimb anatomy strongly suggest that the Malayan tapir possesses obligate function of its lateral fifth digit (Earle, ; MacLaren & Nauwelaerts, ; MacLaren et al. ), akin to some of the earliest extinct tetradactyl (four‐toed) perissodactyls, such as Propalaeotherium (Palaeotheriidae), Lophiodon (Lophiodontidae), Palaeosyops (Brontotheriidae) (Gregory, ; Holbrook, ; Franzen, ), and the ancestors of modern equids (e.g. Sifrhippus ; Froehlich, ; Wood et al.…”

Section: Introductionmentioning

confidence: 99%

“…The Malayan tapir (Tapirus indicus Desmaret) represents the largest of the four widely accepted extant tapir species (Quse & Fernandes-Santos, 2014). Malayan tapirs are considered to have diverged from the lineage which led to the modern neotropical tapirs approximately 25 Mya (Steiner & Ryder, 2011;MacLaren et al 2018). The cranial and postcranial elements have for many years been known to differ from those of neotropical taxa (Earle, 1893), with recent quantitative analyses demonstrating clear divergences between Malayan and neotropical tapir osteology (MacLaren & Nauwelaerts, 2016Dumb a et al 2018).…”

Section: Introductionmentioning

confidence: 99%

“…The cranial and postcranial elements have for many years been known to differ from those of neotropical taxa (Earle, 1893), with recent quantitative analyses demonstrating clear divergences between Malayan and neotropical tapir osteology (MacLaren & Nauwelaerts, 2016Dumb a et al 2018). Morphological comparisons of the forelimb anatomy strongly suggest that the Malayan tapir possesses obligate function of its lateral fifth digit (Earle, 1893;MacLaren & Nauwelaerts, 2017;MacLaren et al 2018), akin to some of the earliest extinct tetradactyl (four-toed) perissodactyls, such as Propalaeotherium (Palaeotheriidae), Lophiodon (Lophiodontidae), Palaeosyops (Brontotheriidae) (Gregory, 1929;Holbrook, 2009;Franzen, 2010), and the ancestors of modern equids (e.g. Sifrhippus;Froehlich, 2002;Wood et al 2011;Secord et al 2012).…”

Section: Introductionmentioning

confidence: 99%

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Comparative forelimb myology and muscular architecture of a juvenile Malayan tapir (Tapirus indicus)

Maclaren

McHorse

2019

Journal of Anatomy

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The absence of preserved soft tissues in the fossil record is frequently a hindrance for palaeontologists wishing to investigate morphological shifts in key skeletal systems, such as the limbs. Understanding the soft tissue composition of modern species can aid in understanding changes in musculoskeletal features through evolution, including those pertaining to locomotion. Establishing anatomical differences in soft tissues utilising an extant phylogenetic bracket can, in turn, assist in interpreting morphological changes in hard tissues and modelling musculoskeletal movements during evolutionary transitions (e.g. digit reduction in perissodactyls). Perissodactyls (horses, rhinoceroses, tapirs and their relatives) are known to have originated with a four‐toed (tetradactyl) forelimb condition. Equids proceeded to reduce all but their central digit, resulting in monodactyly, whereas tapirs retained the ancestral tetradactyl state. The modern Malayan tapir (Tapirus indicus) has been shown to exhibit fully functional tetradactyly in its forelimb, more so than any other tapir, and represents an ideal case‐study for muscular arrangement and architectural comparison with the highly derived monodactyl Equus. Here, we present the first quantification of muscular architecture of a tetradactyl perissodactyl (T. indicus), and compare it to measurements from modern monodactyl caballine horse (Equus ferus caballus). Each muscle of the tapir forelimb was dissected out from a cadaver and measured for architectural properties: muscle‐tendon unit (MTU) length, MTU mass, muscle mass, pennation angle, and resting fibre length. Comparative parameters [physiological cross‐sectional area (PCSA), muscle volume, and % muscle mass] were then calculated from the raw measurements. In the shoulder region, the infraspinatus of T. indicus exhibits dual origination sites on either side of the deflected scapular spine. Within ungulates, this condition has only been previously reported in suids. Differences in relative contribution to limb muscle mass between T. indicus and Equus highlight forelimb muscles that affect mobility in the lateral and medial digits (e.g. extensor digitorum lateralis). These muscles were likely reduced in equids during their evolutionary transition from tetradactyl forest‐dwellers to monodactyl, open‐habitat specialists. Patterns of PCSA across the forelimb were similar between T. indicus and Equus, with the notable exceptions of the biceps brachii and flexor carpi ulnaris, which were much larger in Equus. The differences observed in PCSA between the tapir and horse forelimb muscles highlight muscles that are essential for maintaining stability in the monodactyl limb while moving at high speeds. This quantitative dataset of muscle architecture in a functionally tetradactyl perissodactyl is a pivotal first step towards reconstructing the locomotor capabilities of extinct, four‐toed ancestors of modern perissodactyls, and providing further insights into the equid locomotor transition.

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“…The use of quantitative methods such as three dimensional geometric morphometrics (3D GM; Rohlf & Marcus, 1993 ), can give an overview of the morphological variation of bones within a genus ( Cordeiro-Estrela et al, 2008 ; Hautier et al, 2017 ). This tool is also widely used in morphofunctional studies on the appendicular skeleton ( Milne, Vizcaíno & Fernicola, 2009 ; Martín-Serra, Figueirido & Palmqvist, 2014 ; Botton-Divet et al, 2016 ; Maclaren et al, 2018 ) but remains little used in non-avian dinosaur studies ( Hedrick & Dodson, 2013 ; Ratsimbaholison, Felice & O’Connor, 2016 ; Neenan et al, 2018 ). By using anatomical landmarks and sliding semilandmarks of curves and surface ( Gunz & Mitteroecker, 2013 ), 3D GM permits one to quantify, analyze and visualize the morphological variation in a sample by taking into account the overall shape of the bones of interest, even with few anatomically homologous landmarks, such as in limb long bones.…”

Section: Introductionmentioning

confidence: 99%

Disentangling biological variability and taphonomy: shape analysis of the limb long bones of the sauropodomorph dinosaur Plateosaurus

Lefebvre

Allain²,

Houssaye

et al. 2020

PeerJ

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Sauropodomorph dinosaurs constitute a well-studied clade of dinosaurs, notably because of the acquisition of gigantism within this group. The genus Plateosaurus is one of the best-known sauropodomorphs, with numerous remains from various localities. Its tumultuous taxonomic history suggests the relevance of addressing its intrageneric shape variability, mixed with taphonomic modifications of the original bone shape. Here we investigate quantitatively the morphological variation of Plateosaurus occurring at the genus level by studying the shape variation of a sample of limb long bones. By means of 3D geometric morphometrics, the analysis of the uncorrelated variation permits separation of the variation estimated as obviously taphonomically influenced from the more biologically plausible variation. Beyond the dominant taphonomic signal, our approach permits interpretation of the most biologically plausible features, even on anatomical parts influenced by taphonomic deformations. Those features are thus found on a quantitative basis from the variation of samples containing fossil specimens, by taking the impact of taphonomy into account, which is paramount in order to avoid making biologically ambiguous interpretations.

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A morphometric analysis of the forelimb in the genus Tapirus (Perissodactyla: Tapiridae) reveals influences of habitat, phylogeny and size through time and across geographical space

Cited by 20 publications

References 59 publications

Interspecific variation in the limb long bones among modern rhinoceroses—extent and drivers

Interspecific variation in the limb long bones among modern rhinoceroses—extent and drivers

Comparative forelimb myology and muscular architecture of a juvenile Malayan tapir (Tapirus indicus)

Disentangling biological variability and taphonomy: shape analysis of the limb long bones of the sauropodomorph dinosaur Plateosaurus

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