Giant extinct caiman breaks constraint on the axial skeleton of extant crocodylians

Scheyer, Torsten M.; Hutchinson, John R.; Strauss, Olivier; Delfino, Massimo; Carrillo-Briceño, Jorge D.; Sánchez, R.D.; Sánchez‐Villagra, Marcelo R.

doi:10.7554/elife.49972

Cited by 20 publications

(19 citation statements)

References 56 publications

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“…Likewise, according to nearly all recent phylogenetic analyses (Scheyer et al . 2019; Cidade et al . 2020a), the known representatives of the earliest divergent caimanine lineages (i.e.…”

Section: Discussionmentioning

confidence: 99%

Redescription and phylogenetic affinities of the caimanine Eocaiman cavernensis (Crocodylia, Alligatoroidea) from the Eocene of Argentina

Godoy

Cidade

Montefeltro

et al. 2020

Papers in Palaeontology

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A T present, six extant species of Caimaninae are distributed within the genera Caiman, Melanosuchus and Paleosuchus. These are found mostly in South and Central America (the only exception is Caiman crocodilus, the distribution of which extends as far north as southern Mexico; Thorbjarnarson 1992; Brochu 1999, Grigg & Kirshner 2015. Phylogenetically, Caimaninae is defined as the group that includes C. crocodilus and all crocodylians closer to it than to Alligator mississippiensis (Brochu 1999(Brochu , 2003. It belongs to Alligatoroidea, one of the three main lineages of the crown-group Crocodylia, together with Crocodyloidea and Gavialoidea (Brochu 1999(Brochu , 2003.Within Alligatoroidea, the sister group of Caimanine is Alligatorinae, which is currently represented by only two extant species: A. mississippiensis of North America and A. sinensis from China (Grigg & Kirshner 2015). Nevertheless, compared with Caimaninae, the fossil record of Alligatorinae has been historically regarded as much richer (Brochu 2010), with a more widespread geographic distribution and several species documented for the Cenozoic (Brochu 1999(Brochu , 2003 Whiting et al. 2016).In the twenty-first century, however, new discoveries have revealed a higher diversity of Caimanine during the Cenozoic, especially in South America, but also with

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“…Likewise, according to nearly all recent phylogenetic analyses (Scheyer et al . 2019; Cidade et al . 2020a), the known representatives of the earliest divergent caimanine lineages (i.e.…”

Section: Discussionmentioning

confidence: 99%

Redescription and phylogenetic affinities of the caimanine Eocaiman cavernensis (Crocodylia, Alligatoroidea) from the Eocene of Argentina

Godoy

Cidade

Montefeltro

et al. 2020

Papers in Palaeontology

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“…Crown-group crocodylians share the same number of precaudal vertebrae (9 cervical, 15 dorsal, and 2 sacral vertebrae: Reese 1915 ; Mook 1921b ; Hoffstetter and Gasc 1969 ; Iijima and Kubo 2019 ), allowing the body size estimation based on incompletely preserved precaudal vertebrae. Recently, sacralization of the last dorsal vertebra was reported in a Miocene caimanine Purussaurus mirandai ( Scheyer et al. 2019 ), although it would not change the total number of precaudal vertebrae.…”

Section: Introductionmentioning

confidence: 99%

Vertebrae-Based Body Length Estimation in Crocodylians and Its Implication for Sexual Maturity and the Maximum Sizes

Iijima

Kubo

2020

Integrative Organismal Biology

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Body size is fundamental to the physiology and ecology of organisms. Crocodyliforms are no exception, and several methods have been developed to estimate their absolute body sizes from bone measurements. However, species-specific sizes, such as sexually mature sizes and the maximum sizes were not taken into account due to the challenging maturity assessment of osteological specimens. Here, we provide a vertebrae-based method to estimate absolute and species-specific body lengths in crocodylians. Lengths of cervical to anterior caudal centra were measured and relations between the body lengths (snout-vent and total lengths) and lengths of either a single centrum or a series of centra were modeled for extant species. Additionally, states of neurocentral suture closure were recorded for the maturity assessment. Comparisons of total lengths and timings of neurocentral suture closure showed that most extant crocodylians reach sexual maturity before closure of precaudal neurocentral sutures. Centrum lengths of the smallest individuals with closed precaudal neurocentral sutures within species were correlated with the species maximum total lengths in extant taxa; therefore, the upper or lower limit of the species maximum sizes can be determined from centrum lengths and states of neurocentral suture closure. The application of the current method to non-crocodylian crocodyliforms requires similar numbers of precaudal vertebrae, body proportions, and timings of neurocentral suture closure as compared to extant crocodylians.

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“…Hutchinson et al (2019) observed that crocodylian species reduce speed and eventually lose any asymmetrical gait capacity at only moderate sizes (and probably during ontogeny). Giant (1000-3000+ kg; Table S1) extant and extinct Crocodylia can still walk terrestrially and there has been little study of how they maintain this modest capacity (but see Scheyer et al, 2019). Giant rodents are another captivating case study.…”

Section: Water-land Transitions Gravity and Giantsmentioning

confidence: 99%

The evolutionary biomechanics of locomotor function in giant land animals

Hutchinson

2021

Journal of Experimental Biology

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Giant land vertebrates have evolved more than 30 times, notably in dinosaurs and mammals. The evolutionary and biomechanical perspectives considered here unify data from extant and extinct species, assessing current theory regarding how the locomotor biomechanics of giants has evolved. In terrestrial tetrapods, isometric and allometric scaling patterns of bones are evident throughout evolutionary history, reflecting general trends and lineage-specific divergences as animals evolve giant size. Added to data on the scaling of other supportive tissues and neuromuscular control, these patterns illuminate how lineages of giant tetrapods each evolved into robust forms adapted to the constraints of gigantism, but with some morphological variation. Insights from scaling of the leverage of limbs and trends in maximal speed reinforce the idea that, beyond 100–300 kg of body mass, tetrapods reduce their locomotor abilities, and eventually may lose entire behaviours such as galloping or even running. Compared with prehistory, extant megafaunas are depauperate in diversity and morphological disparity; therefore, turning to the fossil record can tell us more about the evolutionary biomechanics of giant tetrapods. Interspecific variation and uncertainty about unknown aspects of form and function in living and extinct taxa still render it impossible to use first principles of theoretical biomechanics to tightly bound the limits of gigantism. Yet sauropod dinosaurs demonstrate that >50 tonne masses repeatedly evolved, with body plans quite different from those of mammalian giants. Considering the largest bipedal dinosaurs, and the disparity in locomotor function of modern megafauna, this shows that even in terrestrial giants there is flexibility allowing divergent locomotor specialisations.

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Giant extinct caiman breaks constraint on the axial skeleton of extant crocodylians

Cited by 20 publications

References 56 publications

Redescription and phylogenetic affinities of the caimanine Eocaiman cavernensis (Crocodylia, Alligatoroidea) from the Eocene of Argentina

Redescription and phylogenetic affinities of the caimanine Eocaiman cavernensis (Crocodylia, Alligatoroidea) from the Eocene of Argentina

Vertebrae-Based Body Length Estimation in Crocodylians and Its Implication for Sexual Maturity and the Maximum Sizes

The evolutionary biomechanics of locomotor function in giant land animals

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