Cranial Ontogeny of the Early Triassic Basal Cynodont Galesaurus planiceps
Cranial Ontogeny of the Early Triassic Basal Cynodont Galesaurus planiceps
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DOI：
10.1002/ar.23473
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发表时间：
2017-02-01
影响因子：
2
通讯作者：
Abdala, Fernando
中科院分区：
文献类型：
--
作者：
Jasinoski, Sandra C.;Abdala, Fernando
记录了 31 个斜头角蜥蜴标本头骨和下颌骨的个体发育变化，斜角蜥蜴是南非早三叠世的一种基础非哺乳类犬齿兽类动物。定性调查表明，颅颌器官在生长过程中发生了八种变化，将样本分为三个个体发育阶段：幼年期、亚成年期和成年期。颅底长度为 90 mm 时，颞区、颧弓、枕骨和下颌骨发生了从亚成体向成体阶段过渡的过程。至少四种形态和异速生长差异将成年标本分为两种形态，表明滑龙属存在性别二态性。差异包括雄性形态的颧弓广泛横向张开，导致眼眶更靠前，而雌性形态的鼻子更窄。这是首次在基础犬齿兽中记录两性二态性，也是首次在非哺乳类犬齿兽中定量记录。滑角龙和更衍生的基础犬齿兽 Thrinaxodon 之间的个体发育比较揭示了矢状嵴发育的时间和程度的差异。在角龙中，位于顶孔后面的后矢状嵴在个体发育中发育相对较晚，而前矢状嵴很少形成，这表明颞肌的前部纤维不如Thrinaxodon发达。相比之下，与咬肌相关的颅下颌特征在滑齿龙的个体发育过程中变得更加发达。内收肌组织的发育似乎是影响这些基础非哺乳类犬齿动物头骨生长的主要因素之一。 Anat Rec，300:353-381，2017。(c) 2016 Wiley periodicals, Inc.
Ontogenetic changes in the skull and mandible of thirty-one specimens of Galesaurus planiceps, a basal non-mammaliaform cynodont from the Early Triassic of South Africa, are documented. The qualitative survey indicated eight changes in the craniomandibular apparatus occurred during growth, dividing the sample into three ontogenetic stages: juvenile, subadult, and adult. Changes in the temporal region, zygomatic arch, occiput, and mandible occurred during the transition from the subadult to adult stage at a basal skull length of 90 mm. At least four morphological and allometric differences divided the adult specimens into two morphs, indicating the presence of sexual dimorphism in Galesaurus. Differences include extensive lateral flaring of the zygomatic arches in the male morph resulting in a more anterior orientation of the orbits, and a narrower snout in the female. This is the first record of sexual dimorphism in a basal cynodont, and the first time it is quantitatively documented in a non-mammaliaform cynodont. An ontogenetic comparison between Galesaurus and the more derived basal cynodont Thrinaxodon revealed differences in the timing and extent of sagittal crest development. In Galesaurus, the posterior sagittal crest, located behind the parietal foramen, developed relatively later in ontogeny, and the anterior sagittal crest rarely formed suggesting the anterior fibres of the temporalis were less developed than in Thrinaxodon. In contrast, craniomandibular features related to the masseters became more developed during the ontogeny of Galesaurus. The development of the adductor musculature appears to be one of the main factors influencing skull growth in these basal non-mammaliaform cynodonts. Anat Rec, 300:353-381, 2017. (c) 2016 Wiley Periodicals, Inc.