Lara Bennati‐Madureira, Gabriel Leandro Gomes, Kellen Adriana Curci Daros, André Luis da Silva Casas
Little is known about the biology of pygmy sperm whales, Kogia breviceps (De Blainville, 1838), being that most anatomical descriptions for the species derive from necropsy after stranding or from osteological material preserved in museums. This species is rarely seen despite its wide distribution, and its reproductive behaviour is still being investigated. The eventual occurrence of pregnant female strandings and the collection and description of foetuses can give clues about the organisms' mostly unknown early development. However, this type of biological material is extremely rare, limiting anatomical analysis due to the risk of damage or loss. Here, we describe the external and internal anatomy of an 84 cm long K. breviceps foetus. The methods utilised were non‐intrusive, meaning that no incisions were made on the specimen. The foetus was analysed using computed tomography images and a three‐dimensional reconstruction of the skeleton. A great number of features were observed, such as axial and appendicular skeletal structures, internal organs, echolocation apparatus and umbilical cord, as well as diagnostic characters of the species, such as the asymmetrical skull, spermaceti chamber and false gill pigmentation. We suggest that more specimens on different stages of development should be analysed by the same technique, as well as further comparison with specimens from other taxa, in order to facilitate more comparative studies on embryonic and foetal development of cetaceans.
人们对侏儒抹香鲸(Kogia breviceps,De Blainville,1838 年)的生物学知之甚少,对该物种的解剖学描述大多来自搁浅后的尸体解剖或保存在博物馆中的骨骼材料。尽管该物种分布广泛,但却很少见,其繁殖行为仍在研究之中。最终出现的怀孕雌性搁浅以及对胎儿的收集和描述可以提供有关该生物大部分未知的早期发育的线索。然而,这类生物材料极为罕见,由于存在损坏或丢失的风险,限制了解剖分析。在这里,我们描述了一个 84 厘米长的 K. breviceps 胎儿的外部和内部解剖结构。采用的方法是非侵入性的,即不在标本上做任何切口。使用计算机断层扫描图像和骨骼三维重建对胎儿进行了分析。我们观察到了大量特征,如轴向和附着骨骼结构、内脏器官、回声定位装置和脐带,以及该物种的诊断特征,如不对称头骨、精囊腔和假鳃色素沉着。我们建议采用同样的技术对更多不同发育阶段的标本进行分析,并与其他类群的标本作进一步比较,以便对鲸目动物的胚胎和胎儿发育进行更多的比较研究。
{"title":"Anatomical description of a pygmy sperm whale, Kogia breviceps (Cetacea: Kogiidae), pre‐term calf using CT scan and 3D reconstructions","authors":"Lara Bennati‐Madureira, Gabriel Leandro Gomes, Kellen Adriana Curci Daros, André Luis da Silva Casas","doi":"10.1002/ar.25573","DOIUrl":"https://doi.org/10.1002/ar.25573","url":null,"abstract":"Little is known about the biology of pygmy sperm whales, <jats:italic>Kogia breviceps</jats:italic> (De Blainville, 1838), being that most anatomical descriptions for the species derive from necropsy after stranding or from osteological material preserved in museums. This species is rarely seen despite its wide distribution, and its reproductive behaviour is still being investigated. The eventual occurrence of pregnant female strandings and the collection and description of foetuses can give clues about the organisms' mostly unknown early development. However, this type of biological material is extremely rare, limiting anatomical analysis due to the risk of damage or loss. Here, we describe the external and internal anatomy of an 84 cm long <jats:italic>K. breviceps</jats:italic> foetus. The methods utilised were non‐intrusive, meaning that no incisions were made on the specimen. The foetus was analysed using computed tomography images and a three‐dimensional reconstruction of the skeleton. A great number of features were observed, such as axial and appendicular skeletal structures, internal organs, echolocation apparatus and umbilical cord, as well as diagnostic characters of the species, such as the asymmetrical skull, spermaceti chamber and false gill pigmentation. We suggest that more specimens on different stages of development should be analysed by the same technique, as well as further comparison with specimens from other taxa, in order to facilitate more comparative studies on embryonic and foetal development of cetaceans.","PeriodicalId":22308,"journal":{"name":"The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology","volume":"82 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
East Mesa, an Eocene locality situated east of the Shara Murun River in the Erlian Basin, is characterized by basal lower red mudstones. However, a distinct depositional hiatus has been observed in these red mudstones, leading to their division into layers 1 and 2. Excitingly, recent discoveries respectively in layers 1 and 2 of the lower red mudstones at the East Mesa include new Glires (Gomphos sp.) and rodents such as Asiomys dawsoni, Gobiocylindrodon cf. G. ulausuensis, and Yuomys sp., marking their first occurrences within these horizons. A comparative analysis of small mammal faunas suggests that layer 1 may correspond to the Arshantan age, while layer 2 indicates a late Irdinmanhan age based on the combination of taxa found.
{"title":"New Glires materials from the East Mesa, Erlian Basin (Nei Mongol, China)","authors":"Qian Li","doi":"10.1002/ar.25462","DOIUrl":"https://doi.org/10.1002/ar.25462","url":null,"abstract":"East Mesa, an Eocene locality situated east of the Shara Murun River in the Erlian Basin, is characterized by basal lower red mudstones. However, a distinct depositional hiatus has been observed in these red mudstones, leading to their division into layers 1 and 2. Excitingly, recent discoveries respectively in layers 1 and 2 of the lower red mudstones at the East Mesa include new Glires (<jats:italic>Gomphos</jats:italic> sp.) and rodents such as <jats:italic>Asiomys dawsoni</jats:italic>, <jats:italic>Gobiocylindrodon</jats:italic> cf. <jats:italic>G. ulausuensis</jats:italic>, and <jats:italic>Yuomys</jats:italic> sp., marking their first occurrences within these horizons. A comparative analysis of small mammal faunas suggests that layer 1 may correspond to the Arshantan age, while layer 2 indicates a late Irdinmanhan age based on the combination of taxa found.","PeriodicalId":22308,"journal":{"name":"The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140830315","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Elongated upper canine teeth, commonly known as saber‐teeth, have evolved three times within the sub‐order Feliformia. The species that wielded them flourished throughout the Cenozoic and have historically been separated into two morphological groups: the dirk‐tooths with longer, flatter canines, and the scimitar‐tooths with shorter, serrated teeth. However, quantitative morphological analysis has not been conducted on these teeth to determine the true amount of diversity within the group, and how the upper canine morphology of extant feliforms compared to their extinct relatives has also not been explored. Using Geometric Morphometric analysis, it is shown that saber‐tooth upper canine morphology is exceptionally diverse, with no extant clade having all its members occupy the same morphospace based on tooth length and curvature. Instead, a neutral basal morphospace is observed for all groups and diversification from this basal position is seen as species become more derived. A distinct and consistent scimitar tooth morphology is also not observed within the morphospace. When compared with extant taxa, several saber‐tooth species are seen to be morphologically similar to extant feliforms, several of which exhibit novel dietary strategies in comparison to the obligate carnivore felids. Biomechanical analyses of different actual and theoretical tooth shapes demonstrate that saber‐teeth upper canines further represent a functional compromise between sharpness, curvature, and length on the one hand, and robustness and material investment on the other.
{"title":"Morphological diversity of saber‐tooth upper canines and its functional implications","authors":"Caitlin D. Shelbourne, Stephan Lautenschlager","doi":"10.1002/ar.25458","DOIUrl":"https://doi.org/10.1002/ar.25458","url":null,"abstract":"Elongated upper canine teeth, commonly known as saber‐teeth, have evolved three times within the sub‐order Feliformia. The species that wielded them flourished throughout the Cenozoic and have historically been separated into two morphological groups: the dirk‐tooths with longer, flatter canines, and the scimitar‐tooths with shorter, serrated teeth. However, quantitative morphological analysis has not been conducted on these teeth to determine the true amount of diversity within the group, and how the upper canine morphology of extant feliforms compared to their extinct relatives has also not been explored. Using Geometric Morphometric analysis, it is shown that saber‐tooth upper canine morphology is exceptionally diverse, with no extant clade having all its members occupy the same morphospace based on tooth length and curvature. Instead, a neutral basal morphospace is observed for all groups and diversification from this basal position is seen as species become more derived. A distinct and consistent scimitar tooth morphology is also not observed within the morphospace. When compared with extant taxa, several saber‐tooth species are seen to be morphologically similar to extant feliforms, several of which exhibit novel dietary strategies in comparison to the obligate carnivore felids. Biomechanical analyses of different actual and theoretical tooth shapes demonstrate that saber‐teeth upper canines further represent a functional compromise between sharpness, curvature, and length on the one hand, and robustness and material investment on the other.","PeriodicalId":22308,"journal":{"name":"The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology","volume":"80 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140636422","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Holly N. Woodward, Paul Aubier, Mariana Valéria Araújo de Sena, Jorge Cubo
The clade Pseudosuchia appeared 250 million years ago. The exclusively semi‐aquatic Crocodylia, which includes crocodiles, alligators, caimans, and gharials is the only surviving subgroup. Investigating Crocodylia biology is pivotal for inferring traits of extinct pseudosuchians. Alligator femur length is widely used for modeling pseudosuchian body mass, but the regression is influenced by sex and captivity status, leading to potential accuracy problems. An alternative model results from the correlation between alligator femur volume and body mass, which is unaffected by those covariates. Here, an alligator femur volume‐based regression is applied to estimate the masses of non‐crocodylian pseudosuchians, encompassing goniopholids, dyrosaurs, notosuchians, and thalattosuchians. For each, femur volume as the predictor yields lower body masses than does femur length. Morphological resemblances to existing crocodylians support the inference that extinct goniopholids and dyrosaurs were semi‐aquatic. Therefore, body masses predicted from femur length and volume should be reasonable, although larger body masses obtained from femur length may reflect sensitivity to sex or environmental factors. Fully terrestrial notosuchians had proportionately longer femora for their body sizes compared to semi‐aquatic crocodylians, suggesting that the higher body masses predicted from alligator femur length are overestimates. Fully aquatic thalattosuchians, skeletally adapted for buoyancy and with reduced reliance on the femur for locomotion, pose challenges for both femur length and volume‐based models. The results of this study advocate for the use of femur volume to predict body mass, particularly for semi‐aquatic and terrestrial pseudosuchians, and encourage further exploration of volumetric models as body size predictors for extinct vertebrates.
{"title":"Evaluating extinct pseudosuchian body mass estimates using a femur volume‐based model","authors":"Holly N. Woodward, Paul Aubier, Mariana Valéria Araújo de Sena, Jorge Cubo","doi":"10.1002/ar.25452","DOIUrl":"https://doi.org/10.1002/ar.25452","url":null,"abstract":"The clade Pseudosuchia appeared 250 million years ago. The exclusively semi‐aquatic Crocodylia, which includes crocodiles, alligators, caimans, and gharials is the only surviving subgroup. Investigating Crocodylia biology is pivotal for inferring traits of extinct pseudosuchians. <jats:italic>Alligator</jats:italic> femur length is widely used for modeling pseudosuchian body mass, but the regression is influenced by sex and captivity status, leading to potential accuracy problems. An alternative model results from the correlation between alligator femur volume and body mass, which is unaffected by those covariates. Here, an alligator femur volume‐based regression is applied to estimate the masses of non‐crocodylian pseudosuchians, encompassing goniopholids, dyrosaurs, notosuchians, and thalattosuchians. For each, femur volume as the predictor yields lower body masses than does femur length. Morphological resemblances to existing crocodylians support the inference that extinct goniopholids and dyrosaurs were semi‐aquatic. Therefore, body masses predicted from femur length and volume should be reasonable, although larger body masses obtained from femur length may reflect sensitivity to sex or environmental factors. Fully terrestrial notosuchians had proportionately longer femora for their body sizes compared to semi‐aquatic crocodylians, suggesting that the higher body masses predicted from alligator femur length are overestimates. Fully aquatic thalattosuchians, skeletally adapted for buoyancy and with reduced reliance on the femur for locomotion, pose challenges for both femur length and volume‐based models. The results of this study advocate for the use of femur volume to predict body mass, particularly for semi‐aquatic and terrestrial pseudosuchians, and encourage further exploration of volumetric models as body size predictors for extinct vertebrates.","PeriodicalId":22308,"journal":{"name":"The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140623020","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Borja Figueirido, Shane Tucker, Stephan Lautenschlager
Saber‐tooths, extinct apex predators with long and blade‐like upper canines, have appeared iteratively at least five times in the evolutionary history of vertebrates. Although saber‐tooths exhibit a relatively diverse range of morphologies, it is widely accepted that all killed their prey using the same predatory behavior. In this study, we CT‐scanned the skull of Barbourofelis fricki and compared its cranial mechanics using finite element analysis (FEA) with that of Smilodon fatalis. Our aim was to investigate potential variations in killing behavior between two dirk‐toothed sabretooths from the Miocene and Pleistocene of North America. The study revealed that B. fricki had a stoutly‐built skull capable of withstanding stress in various prey‐killing scenarios, while the skull of S. fatalis appeared less optimized for supporting stress, which highlights the highly derived saber‐tooth morphology of the former. The results may indicate that B. fricki was more of a generalist in prey‐killing compared to S. fatalis, which experiences lower stresses under stabbing loads. We hypothesize that morphological specialization in saber‐tooths does not necessarily indicate ecological specialization. Our results support the notion that morphological convergence among saber‐toothed cats may obscure differences in hunting strategies employed to dispatch their prey. Our findings challenge the assumption of the universally assumed canine‐shear biting as the prey‐killing behavior of all saber‐toothed cats. However, further research involving a wider range of dirk and scimitar‐toothed forms could provide additional insights into the diversity of cranial biomechanics within this fascinating group of extinct mammalian predators.
{"title":"Comparing cranial biomechanics between Barbourofelis fricki and Smilodon fatalis: Is there a universal killing‐bite among saber‐toothed predators?","authors":"Borja Figueirido, Shane Tucker, Stephan Lautenschlager","doi":"10.1002/ar.25451","DOIUrl":"https://doi.org/10.1002/ar.25451","url":null,"abstract":"Saber‐tooths, extinct apex predators with long and blade‐like upper canines, have appeared iteratively at least five times in the evolutionary history of vertebrates. Although saber‐tooths exhibit a relatively diverse range of morphologies, it is widely accepted that all killed their prey using the same predatory behavior. In this study, we CT‐scanned the skull of <jats:italic>Barbourofelis fricki</jats:italic> and compared its cranial mechanics using finite element analysis (FEA) with that of <jats:italic>Smilodon fatalis</jats:italic>. Our aim was to investigate potential variations in killing behavior between two dirk‐toothed sabretooths from the Miocene and Pleistocene of North America. The study revealed that <jats:italic>B. fricki</jats:italic> had a stoutly‐built skull capable of withstanding stress in various prey‐killing scenarios, while the skull of <jats:italic>S. fatalis</jats:italic> appeared less optimized for supporting stress, which highlights the highly derived saber‐tooth morphology of the former. The results may indicate that <jats:italic>B. fricki</jats:italic> was more of a generalist in prey‐killing compared to <jats:italic>S. fatalis</jats:italic>, which experiences lower stresses under stabbing loads. We hypothesize that morphological specialization in saber‐tooths does not necessarily indicate ecological specialization. Our results support the notion that morphological convergence among saber‐toothed cats may obscure differences in hunting strategies employed to dispatch their prey. Our findings challenge the assumption of the universally assumed canine‐shear biting as the prey‐killing behavior of all saber‐toothed cats. However, further research involving a wider range of dirk and scimitar‐toothed forms could provide additional insights into the diversity of cranial biomechanics within this fascinating group of extinct mammalian predators.","PeriodicalId":22308,"journal":{"name":"The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology","volume":"38 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140560639","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Andrea Guerrero, Francisco Ortega, Santiago Martín de Jesús, Adán Pérez‐García
Testudines are one of the best‐represented taxonomic groups among the Paleogene taxa of the Duero Basin (Castile and Leon Autonomous Community, central Spain). Among them, Neochelys (Podocnemidide) and Allaeochelys (Carettochelyidae) are most abundant, allowing the population to be assessed for osteological anomalies. The abundance of postcranial remains of both taxa allows us to identify several individuals with potential anomalies, mostly in their shells. Some of them have already been described in previous studies, but most of them are still unpublished. The objective of this study is to analyze in detail the anomalous Neochelys and Allaeochelys remains. As a result, different categories of causal agents (such as bacteria, fungi, parasites, or trauma) have been identified as potential producers of the anomalies in these freshwater turtles. Information regarding the pathogenesis and healing stages of some of these anomalies is provided.
{"title":"Postcranial anomalies of Eocene freshwater pleurodiran and cryptodiran turtles from the Spanish Duero Basin","authors":"Andrea Guerrero, Francisco Ortega, Santiago Martín de Jesús, Adán Pérez‐García","doi":"10.1002/ar.25443","DOIUrl":"https://doi.org/10.1002/ar.25443","url":null,"abstract":"Testudines are one of the best‐represented taxonomic groups among the Paleogene taxa of the Duero Basin (Castile and Leon Autonomous Community, central Spain). Among them, <jats:italic>Neochelys</jats:italic> (Podocnemidide) and <jats:italic>Allaeochelys</jats:italic> (Carettochelyidae) are most abundant, allowing the population to be assessed for osteological anomalies. The abundance of postcranial remains of both taxa allows us to identify several individuals with potential anomalies, mostly in their shells. Some of them have already been described in previous studies, but most of them are still unpublished. The objective of this study is to analyze in detail the anomalous <jats:italic>Neochelys</jats:italic> and <jats:italic>Allaeochelys</jats:italic> remains. As a result, different categories of causal agents (such as bacteria, fungi, parasites, or trauma) have been identified as potential producers of the anomalies in these freshwater turtles. Information regarding the pathogenesis and healing stages of some of these anomalies is provided.","PeriodicalId":22308,"journal":{"name":"The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140560356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Benoit, R. Araujo, E. S. Lund, A. Bolton, T. Lafferty, Z. Macungo, V. Fernandez
Non‐mammaliaform synapsids (NMS) represent the closest relatives of today's mammals among the early amniotes. Exploring their brain and nervous system is key to understanding how mammals evolved. Here, using CT and Synchrotron scanning, we document for the first time three extreme cases of neurosensory and behavioral adaptations that probe into the wide range of unexpected NMS paleoneurological diversity. First, we describe adaptations to low‐frequency hearing and low‐light conditions in the non‐mammalian cynodont Cistecynodon parvus, supporting adaptations to an obligatory fossorial lifestyle. Second, we describe the uniquely complex and three‐dimensional maxillary canal morphology of the biarmosuchian Pachydectes elsi, which suggests that it may have used its cranial bosses for display or low‐energy combat. Finally, we introduce a paleopathology found in the skull of Moschognathus whaitsi. Since the specimen was not fully grown, this condition suggests the possibility that this species might have engaged in playful fighting as juveniles—a behavior that is both social and structured. Additionally, this paper discusses other evidence that could indicate that tapinocephalid dinocephalians were social animals, living and interacting closely with one another. Altogether, these examples evidence the wide range of diversity of neurological structures and complex behavior in NMS.
{"title":"Early synapsids neurosensory diversity revealed by CT and synchrotron scanning","authors":"J. Benoit, R. Araujo, E. S. Lund, A. Bolton, T. Lafferty, Z. Macungo, V. Fernandez","doi":"10.1002/ar.25445","DOIUrl":"https://doi.org/10.1002/ar.25445","url":null,"abstract":"Non‐mammaliaform synapsids (NMS) represent the closest relatives of today's mammals among the early amniotes. Exploring their brain and nervous system is key to understanding how mammals evolved. Here, using CT and Synchrotron scanning, we document for the first time three extreme cases of neurosensory and behavioral adaptations that probe into the wide range of unexpected NMS paleoneurological diversity. First, we describe adaptations to low‐frequency hearing and low‐light conditions in the non‐mammalian cynodont <jats:italic>Cistecynodon parvus</jats:italic>, supporting adaptations to an obligatory fossorial lifestyle. Second, we describe the uniquely complex and three‐dimensional maxillary canal morphology of the biarmosuchian <jats:italic>Pachydectes elsi</jats:italic>, which suggests that it may have used its cranial bosses for display or low‐energy combat. Finally, we introduce a paleopathology found in the skull of <jats:italic>Moschognathus whaitsi</jats:italic>. Since the specimen was not fully grown, this condition suggests the possibility that this species might have engaged in playful fighting as juveniles—a behavior that is both social and structured. Additionally, this paper discusses other evidence that could indicate that tapinocephalid dinocephalians were social animals, living and interacting closely with one another. Altogether, these examples evidence the wide range of diversity of neurological structures and complex behavior in NMS.","PeriodicalId":22308,"journal":{"name":"The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140560353","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sabertoothed mammalian predators, all now extinct, were almost exclusively feloid carnivorans (Eutheria, Placentalia): here a couple of extinct metatherian predators are considered in comparison with the placental sabertooths. Thylacosmilus (the “marsupial sabertooth”) and Thylacoleo (the “marsupial lion”) were both relatively large (puma‐sized) carnivores of the Plio‐Pleistocene in the Southern Hemisphere (Argentina and Australia, respectively). Both carnivores have captured the public imagination, especially as predators that were somehow analogous to northern placental forms. But a more detailed consideration of their morphology shows that neither can be simply analogized with its supposed placental counterpart. While Thylacosmilus did indeed have saber‐like canines, many aspects of its anatomy show that it could not have killed prey in the manner proposed for the sabertoothed felids such as Smilodon. Rather than being an active predator, it may have been a specialized scavenger, using the hypertrophied canines to open carcasses, and perhaps deployed a large tongue to extract the innards. Thylacoleo lacked canines, and its supposedly “caniniform” incisors could not have acted like a felid's canines. Nevertheless, while its mode of dispatching its prey remains a subject for debate, it was clearly a powerful predator, likely to be capable of bringing down prey bigger than itself while hunting alone. In that regard, it may have filled the ecomorphological role proposed for placental sabertooths, and so despite the lack of canines can be nominated as the true “marsupial sabertooth” out of the two extinct taxa.
{"title":"Who was the real sabertooth predator: Thylacosmilus or Thylacoleo?","authors":"Christine M. Janis","doi":"10.1002/ar.25444","DOIUrl":"https://doi.org/10.1002/ar.25444","url":null,"abstract":"Sabertoothed mammalian predators, all now extinct, were almost exclusively feloid carnivorans (Eutheria, Placentalia): here a couple of extinct metatherian predators are considered in comparison with the placental sabertooths. <jats:italic>Thylacosmilus</jats:italic> (the “marsupial sabertooth”) and <jats:italic>Thylacoleo</jats:italic> (the “marsupial lion”) were both relatively large (puma‐sized) carnivores of the Plio‐Pleistocene in the Southern Hemisphere (Argentina and Australia, respectively). Both carnivores have captured the public imagination, especially as predators that were somehow analogous to northern placental forms. But a more detailed consideration of their morphology shows that neither can be simply analogized with its supposed placental counterpart. While <jats:italic>Thylacosmilus</jats:italic> did indeed have saber‐like canines, many aspects of its anatomy show that it could not have killed prey in the manner proposed for the sabertoothed felids such as <jats:italic>Smilodon</jats:italic>. Rather than being an active predator, it may have been a specialized scavenger, using the hypertrophied canines to open carcasses, and perhaps deployed a large tongue to extract the innards. <jats:italic>Thylacoleo</jats:italic> lacked canines, and its supposedly “caniniform” incisors could not have acted like a felid's canines. Nevertheless, while its mode of dispatching its prey remains a subject for debate, it was clearly a powerful predator, likely to be capable of bringing down prey bigger than itself while hunting alone. In that regard, it may have filled the ecomorphological role proposed for placental sabertooths, and so despite the lack of canines can be nominated as the true “marsupial sabertooth” out of the two extinct taxa.","PeriodicalId":22308,"journal":{"name":"The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140560258","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The canine of saber‐toothed predators represents one of the most specialized dental structures known. Hypotheses about the function of hypertrophied canines range from display and conspecific interaction, soft food processing, to active prey acquisition. Recent research on the ontogenetic timing of skull traits indicates the adult canine can take years to fully erupt, but the consequences of prolonged eruption on inferences of canine functional morphology are missing from current discourse and have not been quantified. Here I evaluate hypotheses about adult canine bending strength and stiffness, respectively, during eruption in the felid Smilodon fatalis. Simulated eruption sequences of three adult canines were generated from specimen models to assess shifting cross‐sectional geometry properties, and bending strength and stiffness under laterally directed loads were estimated using finite element analysis. Consistent with beam theory expectations, S. fatalis canine cross‐sectional geometry is optimized for increased bending strength with increased erupted height. However, canine cross‐sectional geometry changes through eruption exaggerate rather than minimize lateral deflection. Spatial constraint for maximum root length from adjacent sensory structures in the maxilla and the recently identified universal power law are hypothesized to limit the growth capacity of canine anteroposterior length and, consequently, maintenance of bending stiffness through eruption. Instead, the joint presence of the deciduous and adult canines for >50% of the adult canine eruption period effectively increases canine mediolateral width and brings bending strength and stiffness estimates closer to theoretical optima. Similarly prolonged retention of deciduous canines in other sabertooths suggests dual‐canine buttressing is a convergently evolved strategy to maximize bending strength and stiffness.
{"title":"Bending performance changes during prolonged canine eruption in saber‐toothed carnivores: A case study of Smilodon fatalis","authors":"Z. Jack Tseng","doi":"10.1002/ar.25447","DOIUrl":"https://doi.org/10.1002/ar.25447","url":null,"abstract":"The canine of saber‐toothed predators represents one of the most specialized dental structures known. Hypotheses about the function of hypertrophied canines range from display and conspecific interaction, soft food processing, to active prey acquisition. Recent research on the ontogenetic timing of skull traits indicates the adult canine can take years to fully erupt, but the consequences of prolonged eruption on inferences of canine functional morphology are missing from current discourse and have not been quantified. Here I evaluate hypotheses about adult canine bending strength and stiffness, respectively, during eruption in the felid <jats:italic>Smilodon fatalis</jats:italic>. Simulated eruption sequences of three adult canines were generated from specimen models to assess shifting cross‐sectional geometry properties, and bending strength and stiffness under laterally directed loads were estimated using finite element analysis. Consistent with beam theory expectations, <jats:italic>S. fatalis</jats:italic> canine cross‐sectional geometry is optimized for increased bending strength with increased erupted height. However, canine cross‐sectional geometry changes through eruption exaggerate rather than minimize lateral deflection. Spatial constraint for maximum root length from adjacent sensory structures in the maxilla and the recently identified universal power law are hypothesized to limit the growth capacity of canine anteroposterior length and, consequently, maintenance of bending stiffness through eruption. Instead, the joint presence of the deciduous and adult canines for >50% of the adult canine eruption period effectively increases canine mediolateral width and brings bending strength and stiffness estimates closer to theoretical optima. Similarly prolonged retention of deciduous canines in other sabertooths suggests dual‐canine buttressing is a convergently evolved strategy to maximize bending strength and stiffness.","PeriodicalId":22308,"journal":{"name":"The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology","volume":"167 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140560256","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}