Telizhenko Valeriia, Gol'din Pavel
Schmalhausen Institute of Zoology, Kyiv, Ukraine.
Sci Rep. 2025 Mar 25;15(1):10268. doi: 10.1038/s41598-025-95566-x.
The skulls of cetaceans (whales, dolphins and porpoises) are distinguished by incomplete ossification of cranial sutures during their lifetime. We suggested suture ossification may correlate with the evolution of rarely reported accessory bones and examine the evolutionary patterns of cranial suture ossification and the presence of accessory elements in the skulls of 47 cetacean species and, for comparison, 15 terrestrial artiodactyls (even-hoofed mammals). A strong phylogenetic signal was found for both suture ossification rate and accessory bone presence. Cetaceans were shown to have a lower ossification rate than most terrestrial artiodactyls, except deer (Cervidae) and mouse deer (Tragulidae), which showed somewhat similar patterns. There were also several types of accessory bony elements, some of them first reported in the skulls of cetaceans and in one case, a muntjac deer. These elements (bones and clefts) evolved in the crania with the least number of ossified sutures. They can be identified as novel elements or, some of them, as plesiomorphies rarely seen in mammals but existing in reptiles and other ancestral groups. This leads to breaking a general trend of mammalian evolution: a reversal of Williston's law (reduction in bone number) and the development of new accessory cranial bones. Slowing cranial development rates explain these trends, and feeding mechanics may be a driver of decreasing suture ossification in cetaceans.
鲸类动物（鲸鱼、海豚和鼠海豚）的头骨在其一生中的显著特征是颅缝骨化不完全。我们认为颅缝骨化可能与罕见报道的附属骨骼的进化相关，并研究了47种鲸类动物头骨中颅缝骨化的进化模式以及附属元素的存在情况，作为对比，还研究了15种陆生偶蹄目动物（偶蹄哺乳动物）。在颅缝骨化率和附属骨的存在方面都发现了很强的系统发育信号。结果表明，除了鹿（鹿科）和鼷鹿（鼷鹿科）表现出有些相似的模式外，鲸类动物的骨化率低于大多数陆生偶蹄目动物。还存在几种类型的附属骨元素，其中一些是首次在鲸类动物头骨中报道的，还有一例是在麂的头骨中发现的。这些元素（骨骼和裂隙）在颅缝骨化最少的颅骨中进化。它们可以被识别为新元素，或者其中一些被识别为在哺乳动物中很少见但存在于爬行动物和其他祖先类群中的祖征。这导致打破了哺乳动物进化的一般趋势：威利斯顿定律（骨骼数量减少）的逆转以及新的附属颅骨的发育。颅骨发育速度减缓解释了这些趋势，而摄食机制可能是鲸类动物颅缝骨化减少的一个驱动因素。
