''Cancrinos'' is a genus of

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

closely allied with the

slipper lobster Slipper lobsters are a family (Scyllaridae) of about 90 species of achelate crustaceans, in the Decapoda clade Reptantia, found in all warm oceans and seas. They are not true lobsters, but are more closely related to spiny lobsters and furry lo ...

s. One species is known, ''C. claviger'' from the Jurassic of southern Germany.

Taxonomy

Fossils of ''Cancrinos'' are rare, and their state of preservation is often imperfect. Count

Georg zu Münster Count Georg Ludwig Friedrich Wilhelm zu Münster (german: Georg Graf zu Münster; 17 February 1776 – 23 December 1844) was a German paleontologist. Biography Münster was born on 17 February 1776, in Langelage near Osnabrück. In 1800, he be ...

first described ''Cancrinos'' in 1839, based on material from the

Upper Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the name ...

Solnhofen limestones of southern Germany. He described two species, ''Cancrinos claviger'' and ''C. latipes'', differentiated by the size of the second antennae, but the two are now considered to be

synonyms A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

. Further specimens have been discovered in

Upper Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

lithographic limestone Lithographic limestone is hard limestone that is sufficiently fine-grained, homogeneous and defect free to be used for lithography. Geologists use the term "lithographic texture" to refer to a grain size under 1/250 mm. The term "sublithog ...

s of

Lebanon Lebanon ( , ar, لُبْنَان, translit=lubnān, ), officially the Republic of Lebanon () or the Lebanese Republic, is a country in Western Asia. It is located between Syria to the north and east and Israel to the south, while Cyprus li ...

, and described as a new species, ''C. libanensis''; however, Haug ''et al.'' (2016) made it the type species of a separate genus '' Paracancrinos''.

Classification

Although Münster was unable to discern any living relatives of ''Cancrinos'' during his original description, Reinhard Förster proposed in 1984 that ''Cancrinos'' was a

transitional form A transitional fossil is any fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group. This is especially important where the descendant group is sharply differentiated by gross a ...

between

spiny lobster Spiny lobsters, also known as langustas, langouste, or rock lobsters, are a family (Palinuridae) of about 60 species of achelate crustaceans, in the Decapoda Reptantia. Spiny lobsters are also, especially in Australia, New Zealand, Ireland, So ...

s (Palinuridae) and

s (Scyllaridae).

Description

''Cancrinos'' differs most markedly from other related animals by the form of the second antennae, which are flattened towards the end, approaching the state seen in living slipper lobsters. Unlike living slipper lobsters, however, the flattened, distal parts of the antennae retain the

ancestral state In phylogenetics, a primitive (or ancestral) character, trait, or feature of a lineage or taxon is one that is inherited from the common ancestor of a clade (or clade group) and has undergone little change since. Conversely, a trait that appears ...

of comprising many segments, rather than being reduced to a single element.

Development

Because immature specimens have been found, parts of the

ontogeny Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the egg to adult. The term can also be used to refer to the stu ...

of ''Cancrinos'' are known, although it is unclear whether the smallest specimens are in the ''

puerulus Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow. The ...

'' stage, or are juveniles. Younger specimens have less flattened antennae, more like those of living

s; thus, ''Canrcinos'' exhibits a form of

heterochrony In evolutionary developmental biology, heterochrony is any genetically controlled difference in the timing, rate, or duration of a developmental process in an organism compared to its ancestors or other organisms. This leads to changes in the si ...

known as

peramorphosis In evolutionary developmental biology, heterochrony is any genetically controlled difference in the timing, rate, or duration of a developmental process in an organism compared to its ancestors or other organisms. This leads to changes in the si ...

. This ontogeny is thought to reflect the

phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spec ...

of ''Cancrinos'', representing a partial development from the ancestral spiny lobster-like form towards the derived slipper lobster-like form.

References

External links

* {{Taxonbar, from=Q339550 Achelata Transitional fossils Late Jurassic genus first appearances Late Jurassic genus extinctions Fossil taxa described in 1839