Placoderm Assemblage from the Tetrapod-Bearing Locality of Strud (Belgium, Upper Famennian) Provides Evidence for a Fish Nursery

The placoderm fauna of the upper Famennian tetrapod-bearing locality of Strud, Belgium, includes the antiarch Grossilepis rikiki, the arthrodire groenlandaspidid Turrisaspis strudensis and the phyllolepidid Phyllolepis undulata. Based on morphological and morphometric evidence, the placoderm specimens from Strud are predominantly recognised as immature specimens and this locality as representing a placoderm nursery. The Strud depositional environment corresponds to a channel in an alluvial plain, and the presence of a nursery in such environment could have provided nutrients and protection to the placoderm offspring. This represents one of the earliest pieces of evidence for this sort of habitat partitioning in vertebrate history, with adults living more distantly from the nursery and using the nursery only to spawn or give live birth.

比利时斯特鲁德（Strud）产出四足类（tetrapod）化石的法门宁阶（Famennian）上部化石点的盾皮鱼（placoderm）动物群，包含反甲鱼类（antiarch）的里克基粗鳞鱼（Grossilepis rikiki）、节甲鱼类（arthrodire）的格陵兰盾科（groenlandaspidid）斯特鲁德旋盾鱼（Turrisaspis strudensis）以及叶鳞鱼科（phyllolepidid）波状叶鳞鱼（Phyllolepis undulata）。基于形态学（morphological）与形态测量学（morphometric）证据，斯特鲁德产出的盾皮鱼标本多被认定为未成年个体，该化石点被视作一处盾皮鱼保育场。斯特鲁德的沉积环境对应冲积平原（alluvial plain）中的河道，此类环境中的保育场可为盾皮鱼幼体提供营养与庇护，这也是脊椎动物演化历史中此类生境分区（habitat partitioning）现象的最早实证之一：成体个体栖息于距保育场更远的区域，仅在此产卵或产下活幼体。