The five digits of the giraffe metatarsal
The five digits of the giraffe metatarsal
复制标题
长颈鹿跖骨的五个数字
DOI：
10.1093/biolinnean/blaa136
复制
发表时间：
2020
影响因子：
1.9
通讯作者：
Solounias, Nikos
中科院分区：
文献类型：
--
作者：
Yohe, Laurel R;Solounias, Nikos
进化以特定的方式塑造了有蹄动物的四肢。在偶蹄趾中，人们通常认为跖骨是由第三和第四指融合而成的，而其他三指已经丢失或高度退化。然而，来自化石记录和跖骨内部形态学的证据挑战了这些假设。此外，仅对少数分类类群进行了分析。在长颈鹿身上，我们发现所有的五个手指都在成年的跖骨上，并且高度融合和修饰，而不是丢失。我们检查了两个中新世中期和晚期长颈鹿化石以及现存长颈鹿和霍加狓的跖骨的高分辨率微型计算机断层扫描。在所有分析的长颈鹿科中，我们发现了四种形态的组合：(1)四个关节面；(2)内部有四个或大多数情况下有五个独立的髓腔；(3)一个清晰的小数字I；(4)在两个未知属的化石分类群中，在II和V指的融合处存在外部细长的凹槽。现存的长颈鹿科长颈鹿和多卡皮亚长颈鹿与所有已灭绝的类群的不同之处在于，它们有更多扁平的趾紧密地挤在一起，这表明尽管生态和运动方式不同，但它们的趾高度融合。这些发现提供的证据增强了我们对骨骼如何融合的理解，并对目前关于手指丢失的假设提出了质疑。
Evolution has shaped the limbs of hoofed animals in specific ways. In artiodactyls, it is the common assumption that the metatarsal is composed of the fusion of digits III and IV, whereas the other three digits have been lost or are highly reduced. However, evidence from the fossil record and internal morphology of the metatarsal challenges these assumptions. Furthermore, only a few taxonomic groups have been analysed. In giraffes, we discovered that all five digits are present in the adult metatarsal and are highly fused and modified rather than lost. We examined high-resolution micro-computed tomography scans of the metatarsals of two mid and late Miocene giraffid fossils and the extant giraffe and okapi. In all the Giraffidae analysed, we found a combination of four morphologies: (1) four articular facets; (2) four or, in most cases, five separate medullary cavities internally; (3) a clear, small digit I; and (4) in the two fossil taxa of unknown genus, the presence of external elongated grooves where the fusions of digits II and V have taken place.GiraffaandOkapia, the extant Giraffidae, show a difference from all the extinct taxa in having more flattened digits tightly packed together, suggesting convergent highly fused digits despite divergent ecologies and locomotion. These discoveries provide evidence that enhances our understanding of how bones fuse and call into question current hypotheses of digit loss.
DOI：
10.1098/rspb.2017.1174
发表时间：
2017-08-30
影响因子：
4.7
作者：
McHorse, Brianna K.;Biewener, Andrew A.;Pierce, Stephanie E.
通讯作者：
Pierce, Stephanie E.
影响因子：
9.2
作者：
Fennessy, Julian;Bidon, Tobias;Janke, Axel
通讯作者：
Janke, Axel
DOI：
10.1098/rspb.2019.2756
发表时间：
2020-02-12
影响因子：
4.7
作者：
Kavanagh, Kathryn D.;Bailey, C. Scott;Sears, Karen E.
通讯作者：
Sears, Karen E.