Gorzelak Przemysław, Janiszewska Katarzyna, Hoşgör İzzet, Salamon Mariusz A
Institute of Paleobiology, Polish Academy of Sciences, Twarda 51/55, 00- 818, Warsaw, Poland.
Exploration Department, Turkish Petroleum Corporation (TPAO), 06530, Ankara, Turkey.
Sci Rep. 2025 Aug 26;15(1):31418. doi: 10.1038/s41598-025-16412-8.
During geological history, some crinoids convergently deviated from a benthic lifestyle. Seirocrinus is an iconic example of a crinoid that adapted to a pseudoplanktonic mode of life by living attached to drift logs. While significant effort has been devoted to exploring its functional morphology and palaeoecology, little attention has been given to the microstructural design of its stalk. Here, we describe the stereom microstructure and internal architecture of the Seirocrinus stalk. We demonstrate that its stereom organization closely resembles that observed in extant benthic crinoids (isocrinids): coarse, irregular labyrinthic-like stereom is found in the interpetaloid zones, while the aligned, galleried stereom is extensively developed in the petaloid zones. We show that this galleried stereom displays a distinct Voronoi-like geometrical pattern, enabling strength-to-weight optimization and minimization of calcification costs. In contrast to the stalks of extant isocrinids, however, the seirocrinid stalk exhibits certain skeletal adaptations that reduce the crinoid's weight, such as large intercolumnar cavities. Consequently, the overall weight of these pseudoplanktonic crinoids might have been lower than previously thought, and thus they may not have significantly contributed to the sinking of the raft system, which would have allowed for multi-generational colonization of the log. These results support the hypothesis that the life of the Seirocrinus-bearing raft "colony" was more dependent on the wood structure itself and did not rely heavily on the seirocrinid "colonies" causing overloading.
在地质历史时期，一些海百合类动物趋同地偏离了底栖生活方式。西罗海百合是海百合类动物的一个标志性例子，它通过附着在漂流木上适应了假浮游生活方式。虽然人们已经投入了大量精力来探索其功能形态和古生态学，但对其茎的微观结构设计却很少关注。在这里，我们描述了西罗海百合茎的立体微观结构和内部结构。我们证明，其立体结构组织与现存底栖海百合类动物（等节海百合）中观察到的结构非常相似：花瓣间区域存在粗糙、不规则的迷宫状立体结构，而在花瓣状区域则广泛发育有排列整齐、有通道的立体结构。我们表明，这种有通道的立体结构呈现出一种独特的类似沃罗诺伊的几何图案，能够实现强度与重量的优化以及钙化成本的最小化。然而，与现存等节海百合的茎不同，西罗海百合的茎表现出某些骨骼适应性特征，这些特征减轻了海百合的重量，例如大的柱间腔。因此，这些假浮游海百合类动物的总体重量可能比之前认为的要低，所以它们可能对筏系统的下沉没有显著贡献，这使得原木能够进行多代定殖。这些结果支持了这样一种假设，即携带西罗海百合的筏“群落”的生存更多地依赖于木材结构本身，而不是严重依赖于海百合“群落”导致超载。
