Crustacean from the Rhynie chert: Lepidocaris rhyniensis

This very small crustacean (up to 3 mm) is the most common and best-known animal from the Rhynie chert. It belongs to an extinct order of the branchiopod crustaceans, the Lipostraca, and it is the oldest known species in this group. It is also one of the earliest known freshwater crustaceans.
Lepidocaris rhyniensis had no carapace and the body can be broadly divided into three parts: head, trunk and tail. Mostly disarticulated fragments or clusters of fragments are found, probably moults (exuviae). A lot of development stages and forms are known like female specimens with egg pouch and juvenile animals.
There are no eyes but two pairs of appendages on the head: the antennules, being small and unbranched, and the antennae, being large, dichotomizing and bearing long hairs (setae) at the last articles. Furthermore the animal was in the possession of firm mandibles and a pair of maxillae (modified appendages), attached to a segment fused with the head (B in the drawing below).
The trunk is composed of 14 segments with appendages and 3 segments without appendages. The first two pairs of appendages of the trunk are similar to the maxillae (B). They bear comb-like brushes at the ends. The next eight are more foliaceous in structure and they dichotomize at the top. They have long setae at the top (C and D). The last two pairs of appendages are of a different structure in male and female specimens.
At the end of the tail there are two long projections with setae.
The three anterior appendages were probably used for food-gathering and eating. The next eight appendages formed a filter-feeding system and were used in transporting the food through the food-groove (on the ventral side) to the mouth region and also for swimming.

Go for an extensive description of this species to the website of the University of Aberdeen.

Reconstruction of Lepidocaris rhyniensis

Reconstructions of Lepidocaris rhyniensis by Scourfield 1926. Scale bar = 1 mm.
Scourfield, D. J., 1926. On a new type of crustacean from the old Red Sandstone (Rhynie chert Bed, Aberdeenshire) - Lepidocaris rhyniensis, gen. et sp. nov. - Philosophical Transactions of the Royal Society, London (Series B), 214: 153-187.

Lepidocaris rhyniensis

Appendages of Lepidocaris: A. clasper of a male
B. maxilla-like appendage of the head region C. 6th - 10th pair of appendages
D. 3th - 5th pair of appendages.
pr = protopod, ex = exopod, en = endopod, ed = endites

Lepidocaris rhyniensis

Tail  (telson) of Lepidocaris
pf = primary furcae, sf = secundary furcae
lp = lateral process
Scale bar = 200 µm


Rather complete animal

Rather complete animal with head and appendage

Cluster of moulting remains and a rather complete animal

Spines with comb-like structures on one of the anterior appendages

Brushes on one of the anterior appendages

Spines on trunk appendages