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Morphology and osteohistology of a large‐bodied caenagnathid (Theropoda, Oviraptorosauria) from the Hell Creek Formation (Montana): implications for size‐based classifications and growth reconstruction in theropods
Papers in Palaeontology ( IF 2.3 ) Pub Date : 2020-03-18 , DOI: 10.1002/spp2.1302
Thomas M. Cullen 1 , D. Jade Simon 2, 3 , Elizabeth K. C. Benner 2 , David C. Evans 2, 3
Affiliation  

Oviraptorosaurs, like many coelurosaurians, are frequently diagnosed using incomplete or fragmentary skeletal remains, with factors such as body size often used to assign material to a particular taxon or as a basis for describing new species. Here we describe a partial skeleton, ROM VP 65884, from the Hell Creek Formation (Montana, USA), and through morphological and phylogenetic comparisons identify it as belonging to Caenagnathidae, and probably referable to Anzu wyliei. We perform multi‐element osteohistological sampling of the tibia, fibula, manual phalanx, rib and gastralium of ROM VP 65884 to determine the ontogenetic status of the individual, and to perform a detailed assessment of the intra‐skeletal variation present in a series of histological proxies for growth and development. Skeletochronological analysis suggests ROM VP 65884 was still actively growing at time of death. Lacunar area was variable, but consistent with values reported for other dinosaurs and vertebrates. Osteocyte lacunar density was found to be relatively similar to the few previous measurements known from coelurosaurian dinosaurs, and preserved no ontogenetic pattern. Osteocyte lacunar density (OLD) was much higher in sampled rib and gastralia elements when compared to limbs, and the high variability in OLD overall lends further support against the hypothesis of this feature acting as a proxy for mass‐specific growth rate. Our results stress the importance of using osteohistological analyses to constrain variation and permit ontogenetic assessment, and suggest caution be taken when using size as a determinant for referral of disassociated elements to specific or new coelurosaur taxa.

中文翻译:

地狱溪地层(蒙大拿州)的大型犬齿(Theropoda,Oviraptorosauria)的形态和骨组织学:对兽脚类基于大小的分类和生长重建的影响

像许多喙骨龙一样,常常使用不完整或零碎的骨骼遗骸来诊断蛇骨龙,并经常使用身体大小等因素来将物质分配给特定的分类单元或作为描述新物种的基础。在这里,我们描述了来自地狱溪地层(美国蒙大纳州)的部分骨架,ROM VP 65884,并通过形态和系统发育比较将其鉴定为属于Caenagnathidae,并且可能指的是Anzu wyliei。我们对ROM VP 65884的胫骨,腓骨,手动指骨,肋骨和胃进行多元素骨组织学采样,以确定个体的个体发育状态,并对一系列组织学中存在的骨骼内变异进行详细评估增长和发展的代理。骨骼年代学分析表明,ROM VP 65884在死亡时仍处于活跃状态。腔隙面积是可变的,但与其他恐龙和脊椎动物的报道值一致。发现骨细胞腔隙密度与腔棘龙恐龙已知的几项先前测量结果相对相似,并且没有保留任何个体发育模式。与四肢相比,肋骨和胃中元素的骨细胞腔隙密度(OLD)高得多,OLD整体的高度可变性进一步支持了该特征假说代表质量特定增长率的假说。我们的结果强调了使用骨组织学分析来限制变异并允许进行个体发育评估的重要性,并建议在使用大小作为将关联元素推荐给特定或新的腔骨类群的决定因素时要格外小心。
更新日期:2020-03-18
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