Lepidocaris
Encyclopedia
Lepidocaris rhyniensis is an extinct species of crustacean
. It is the only species known from the order Lipostraca, and is the only abundant animal in the Rhynie chert
desposits. It resembles modern Anostraca, to which it is probably closely related, although its relationships to other orders remain unclear. The body is 3 mm (0.118110236220472 in) long, with 23 body segments and 19 pairs of appendage
s, but no carapace
. It occurred chiefly among charophytes, probably in alkaline temporary pools
.
deposits in Aberdeenshire
, Scotland
, which is a famous , or site of exceptional preservation. Lepidocaris is the only abundant animal in the deposits, and is likely to be responsible for many of the frequent coprolite
s found in the rocks.
Lepidocaris was first described
by D. J. Scourfield in a 1926 paper in the Philosophical Transactions of the Royal Society B
. Scourfield could not accommodate his new genus in the same order
as its closest relatives – the Anostraca – so he erected a new family
and order for Lepidocaris alone: Lepidocarididae and Lipostraca, respectively. Until 2003, when Castracollis was described, Lepidocaris was the only crustacean known from the Rhynie chert.
with 23 body segments. The whole body measures around 3 millimetre (0.118110236220472 in) long. The head two pairs of antennae
, the second of which is used for swimming. As in Anostraca, there is no carapace
. There are eleven pairs of appendages on the thorax and abdomen, of which the first eight pairs are similar to the swimming limbs of copepod
s, while the last three pairs are phyllopodia, or leaf-like limbs, as seen in other branchiopods such as Triops
. The tail ends in a pair of caudal furcae.
crustaceans. It is frequently found in association with the charophyte
Palaeonitella (Characeae); if the ecology of Palaeonitella resembled that of its modern relatives, the water would have been alkaline
. Similarly, Lepidocaris is thought to have had a similar ecology to extant members of the Anostraca, such as Artemia, inhabiting shallow, temporary pools
.
was not unthinkable. In 1986, Frederick Schram
considered Lipostraca to be the sister group to Brachypoda, with the two orders together making up the Cephalocarida
. In 1997, Dieter Walossek considered Lepidocaris and Rehbachiella to be stem-group anostracans, outside the extant Euanostraca. In 2001, Schram and Koenemann considered Lepidocaris and Rehbachiella to be stem-group lineages basal to the whole Branchiopoda
.
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
. It is the only species known from the order Lipostraca, and is the only abundant animal in the Rhynie chert
Rhynie chert
The Rhynie chert is an Early Devonian sedimentary deposit exhibiting extraordinary fossil detail or completeness . It is exposed near the village of Rhynie, Aberdeenshire, Scotland; a second unit, the Windyfield chert, is located some 700 m away...
desposits. It resembles modern Anostraca, to which it is probably closely related, although its relationships to other orders remain unclear. The body is 3 mm (0.118110236220472 in) long, with 23 body segments and 19 pairs of appendage
Appendage
In invertebrate biology, an appendage is an external body part, or natural prolongation, that protrudes from an organism's body . It is a general term that covers any of the homologous body parts that may extend from a body segment...
s, but no carapace
Carapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
. It occurred chiefly among charophytes, probably in alkaline temporary pools
Vernal pool
Vernal pools, also called vernal ponds or ephemeral pools, are temporary pools of water. They are usually devoid of fish, and thus allow the safe development of natal amphibian and insect species...
.
Biostratigraphy and taxonomy
All the known specimens of Lepidocaris rhyniensis have been excavated from the Rhynie chertRhynie chert
The Rhynie chert is an Early Devonian sedimentary deposit exhibiting extraordinary fossil detail or completeness . It is exposed near the village of Rhynie, Aberdeenshire, Scotland; a second unit, the Windyfield chert, is located some 700 m away...
deposits in Aberdeenshire
Aberdeenshire
Aberdeenshire is one of the 32 unitary council areas in Scotland and a lieutenancy area.The present day Aberdeenshire council area does not include the City of Aberdeen, now a separate council area, from which its name derives. Together, the modern council area and the city formed historic...
, Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
, which is a famous , or site of exceptional preservation. Lepidocaris is the only abundant animal in the deposits, and is likely to be responsible for many of the frequent coprolite
Coprolite
A coprolite is fossilized animal dung. Coprolites are classified as trace fossils as opposed to body fossils, as they give evidence for the animal's behaviour rather than morphology. The name is derived from the Greek words κοπρος / kopros meaning 'dung' and λιθος / lithos meaning 'stone'. They...
s found in the rocks.
Lepidocaris was first described
Alpha taxonomy
Alpha taxonomy is the discipline concerned with finding, describing and naming species of living or fossil organisms. This field is supported by institutions holding collections of these organisms, with relevant data, carefully curated: such institutes include natural history museums, herbaria and...
by D. J. Scourfield in a 1926 paper in the Philosophical Transactions of the Royal Society B
Philosophical Transactions of the Royal Society B: Biological Sciences
Philosophical Transactions of the Royal Society B: Biological Sciences is a peer-reviewed scientific journal published by the Royal Society. The ISO abbreviation for the journal is Phil. Trans. R. Soc...
. Scourfield could not accommodate his new genus in the same order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
as its closest relatives – the Anostraca – so he erected a new family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
and order for Lepidocaris alone: Lepidocarididae and Lipostraca, respectively. Until 2003, when Castracollis was described, Lepidocaris was the only crustacean known from the Rhynie chert.
Description
Lepidocaris rhyniensis is a segmented animalSegmentation
Segmentation may mean:*Market segmentation, in economics and marketingBiology*A process of morphogenesis that divides a metazoan body into a series of semi-repetitive segments*Segmentation , a series of semi-repetitive segments...
with 23 body segments. The whole body measures around 3 millimetre (0.118110236220472 in) long. The head two pairs of antennae
Antenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
, the second of which is used for swimming. As in Anostraca, there is no carapace
Carapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
. There are eleven pairs of appendages on the thorax and abdomen, of which the first eight pairs are similar to the swimming limbs of copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s, while the last three pairs are phyllopodia, or leaf-like limbs, as seen in other branchiopods such as Triops
Triops
Triops is a genus of small crustaceans in the order Notostraca . They are considered living fossils, with a fossil record that reaches back to the Carboniferous, .-Relatives and fossil record:...
. The tail ends in a pair of caudal furcae.
Ecology
Lepidocaris is one of the earliest preserved freshwaterFresh Water
Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...
crustaceans. It is frequently found in association with the charophyte
Charophyta
The Charophyta are a division of green algae, including the closest relatives of the embryophyte plants. In some groups, such as conjugating green algae, flagellate cells do not occur. The latter group does engage in sexual reproduction, and motility does not involve flagella, since they are...
Palaeonitella (Characeae); if the ecology of Palaeonitella resembled that of its modern relatives, the water would have been alkaline
Alkalinity
Alkalinity or AT measures the ability of a solution to neutralize acids to the equivalence point of carbonate or bicarbonate. The alkalinity is equal to the stoichiometric sum of the bases in solution...
. Similarly, Lepidocaris is thought to have had a similar ecology to extant members of the Anostraca, such as Artemia, inhabiting shallow, temporary pools
Vernal pool
Vernal pools, also called vernal ponds or ephemeral pools, are temporary pools of water. They are usually devoid of fish, and thus allow the safe development of natal amphibian and insect species...
.
Relationships
The phylogenetic position of Lepidocaris in relation to other orders of crustaceans is uncertain. In his original description of the species, Scourfield noted that Lepidocaris could not be accommodated in the existing order Anostraca, and even suggested that a position outside the BranchiopodaBranchiopoda
Branchiopoda is a class of crustaceans. It is the sister group to the remaining crustaceans, and comprises fairy shrimp, clam shrimp, Cladocera, Notostraca and the Devonian Lepidocaris...
was not unthinkable. In 1986, Frederick Schram
Frederick Schram
Frederick Robert Schram is an American palaeontologist and carcinologist. He received his B.S. in biology from Loyola University Chicago in 1965, and a Ph.D...
considered Lipostraca to be the sister group to Brachypoda, with the two orders together making up the Cephalocarida
Cephalocarida
Cephalocarida is a class inside the subphylum Crustacea that comprises only twelve shrimp-like benthic species. They were discovered in 1955 by Howard L. Sanders, and are commonly referred to as horseshoe shrimps. They have been grouped together with the Remipedia in the Xenocarida...
. In 1997, Dieter Walossek considered Lepidocaris and Rehbachiella to be stem-group anostracans, outside the extant Euanostraca. In 2001, Schram and Koenemann considered Lepidocaris and Rehbachiella to be stem-group lineages basal to the whole Branchiopoda
Branchiopoda
Branchiopoda is a class of crustaceans. It is the sister group to the remaining crustaceans, and comprises fairy shrimp, clam shrimp, Cladocera, Notostraca and the Devonian Lepidocaris...
.