'' Lyrarapax'' is a

radiodont Radiodonta is an extinct order of stem-group arthropods that was successful worldwide during the Cambrian period. Radiodonts are distinguished by their distinctive frontal appendages, which are morphologically diverse and were used for a variety ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of the family

Amplectobeluidae ''Amplectobeluidae'' is a clade of Cambrian radiodonts. It currently includes five definitive genera, ''Amplectobelua'', '' Lyrarapax'', '' Ramskoeldia'', '' Guanshancaris'' and a currently unnamed genus from the lower Cambrian aged Sirius Passet ...

that lived in the early

Cambrian The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...

period 518 million years ago. Its fossils were found in the

Maotianshan Shales The Maotianshan Shales () are a series of Early Cambrian sedimentary deposits in the Chiungchussu Formation or Heilinpu Formation, famous for their '' Konservat Lagerstätten'', deposits known for the exceptional preservation of fossilized orga ...

of China. The first species, ''Lyrarapax unguispinus'' was described in 2014, with a second species, ''Lyrarapax trilobus'' being described in 2016, differing principally in the morphology of its frontal appendages.

Description

''L. unguispinus'' is roughly long.Dryad Data
/ref> Its frontal appendages are short with a large first endite bearing several spines and alternating endites thereafter. The neck is prominent with four segments. The first flap pair is hypertrophied and paddle-shaped, with the following pairs decreasing sharply in size and a tail fan composed of three blade-like flap pairs. Remarkably, the nervous system of ''L. unguispinus'' is preserved in detail, showing that radiodont frontal appendages are protocerebral like the antennae of

velvet worm Onychophora (from , , "claws"; and , , "to carry"), commonly known as velvet worms (for their velvety texture and somewhat wormlike appearance) or more ambiguously as peripatus (after the first described genus, '' Peripatus''), is a phylum of e ...

s, showing the two structures derive from the same source. In addition, as the labrum also seems to be protocerebral, it also likely derives from the same structures, providing a possible answer to the

arthropod head problem The (pan)arthropod head problem is a long-standing zoological dispute concerning the Segmentation (biology), segmental composition of the heads of the various arthropod groups, and how they are evolutionarily related to each other. While the dis ...

. ''L. trilobus'' is quite similar, although somewhat smaller, with its H-element having a rimmed margin. The frontal appendages are quite different, with the very presence of endites being alternating (the third and fifth non-shaft podomeres lack them altogether) and the second endite being especially large. Contrary to its initial description reporting an unusual wrinkled structure around the mouth, ''Lyrarapax'' possessed a typical radiodontan oral cone, a radial mouth with four large plates and smalller, thinner plates between them. The first flap in this species is not much wider than the rest, unlike in ''L. unguispinus'', alongside the flaps having transverse lines interpreted as strengthening rays, another trait unique to this species. The trunk is divided into three lobes (giving this species its name) by prominent furrows, with the central region being more raised than the lateral ones.

Etymology

The scientific name "''Lyrarapax''" is a compound word of the Latin "lyra" (lyre) and "rapax" (predator), and is named after the outline of the body of this genus, which resembles a stringed instrument called a

lyre The lyre () (from Greek λύρα and Latin ''lyra)'' is a string instrument, stringed musical instrument that is classified by Hornbostel–Sachs as a member of the History of lute-family instruments, lute family of instruments. In organology, a ...

, as well as its presumed predatory lifestyle. The species name ''unguispinus'' derives from the spiny, claw-like frontal appendages, while ''trilobus'' derives from the three-lobed trunk.

References

{{Taxonbar, from=Q17409525 Fossils of China Radiodonta Fossil taxa described in 2014 Paleontology in Yunnan Prehistoric arthropod genera Cambrian genus extinctions Cambrian arthropods of Asia

Description

Etymology

See also

References