Phacops

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Phacops
Temporal range: Late Ordovician-Late Devonian
~457–360  Ma
Phacops s.jpg
Phacops sp. from the Eifelian of Morocco
Phacops eye.jpg
Phacops sp. eye
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class:† Trilobita
Order:† Phacopida
Family:† Phacopidae
Genus:† Phacops
Emmrich, 1839
Type species
Calymene latifrons
Bronn, 1825
Species

and see text

Synonyms
  • Portlockia
  • Somatrikelon
  • Somatrikopon

Phacops is a genus of trilobites in the order Phacopida, family Phacopidae, that lived in Europe, northwestern Africa, North and South America and China from the Late Ordovician until the very end of the Devonian, [2] with a broader time range described from the Late Ordovician. [3] It was a rounded animal, with a globose head and large eyes, and probably fed on detritus. [4] Phacops is often found rolled up ("volvation"), a biological defense mechanism that is widespread among smaller trilobites but further perfected in this genus. [4]

Contents

Description

Like in all sighted Phacopina, the eyes of Phacops are compounded of very large, separately set lenses without a common cornea (so called schizochroal eyes), and like almost all other Phacopina, the articulate mid-length part of the body (or thorax) in Phacops has 11 segments.

Unknown enrolled Phacops sp. from the Eifelian of Morocco. Enrolled phacops.jpg
Unknown enrolled Phacops sp. from the Eifelian of Morocco.

The central raised area (or glabella) of the headshield (or cephalon) is moderately to strongly inflated near to its front, more or less flattened on the top, falling vertically to or slightly overhanging the border furrow. Up to three lateral furrows may be discernable on the glabella behind the utterly dominating frontal lobe. From the back there is a very distinct occipital ring, and in front of that a distinct preoccipital ring which is weakly divided into a strongly convex central lobe and weakly convex lateral lobes. The large to medium size eyes have a crescent shaped outline, and are elevated high above the cheeks. The steep visual surface is kidney shaped. The back corners of the cephalon (or genal angles) are acutely to bluntly rounded, but a genal spine is lacking in adults. In the ventral surface of the seam (or doublure) is in the frontal half of the cephalon a continuous furrow, delineated by ridges, and with notches laterally. This so-called vindicular furrow serves to lock the rim of the tailshield to the headshield when the trilobite is enrolled.

The axial rings of the thorax do not have convex lateral axial nodes on its outer surface. The tailshield (or pygidium) is well segmented. The pygidial axis has 9 to 11 rings, and the pleural areas to the sides have 5 to 8 pairs of recognizable ribs. Furrows between the ribs are deep, those that divide each rib in frontal and rear bands are very shallow, and the frontal bands are widest. The surface of the exoskeleton is covered in tubercles. [5]

Camouflage

Reconstruction of Phacops with a speculative, cryptic "Rorschach" pattern based on the proposed ability to camouflage. Phacops plate.png
Reconstruction of Phacops with a speculative, cryptic "Rorschach" pattern based on the proposed ability to camouflage.

There are specimens known of Phacops rana with many irregular black spots. Because similar spots in a specimen of Greenops boothi from the same site are arranged in rows, it may be assumed that they are original and not caused by the fossilisation process. The spots are irregular and have spurs branching outwardly, similar to the melanophores in many extant animals. In one specimen, the black spots are much larger than in another one. It is quite conceivable that changing the size of the melanophores enabled Phacops rana to camouflage itself in different environments. [6]

Taxonomy

The concept of many fossil taxa has been tightened over time, including Phacops. As a result, Boeckops, Chotecops, Paciphacops, Prokops and Viaphacops have been erected as subgenera of Phacops, and are now widely regarded as genera in their own right. [7] Most recent, it was considered that some North-American and North-African species on the one hand and European species on the other hand differ sufficiently from each other to be assigned to separate genera. As the type species is the European P. latifrons, the North-American species are now called Eldredgeops . However, the previous assigned species, like Phacops rana , are still widely used among fossil collectors. Eldredgeops has a raised ridge along the ventral margin of the cephalon, the glabella is more inflated, the lateral parts of the preoccipital ring are not round but rectangular, the palpebral area and palpebral lobe are larger than in P. latifrons, and there is no fold right behind the posterior vertical row of lenses, nor an isolated raised area just below the lenses. Not all of these characters may differentiate between Eldredgeops and other Phacops species however. [8]

During the Eifelian in the present-day Belgian Ardennes, several Phacops species developed from each other, the oldest being P. imitator, followed by P. fragosus, then P. latifrons and finally P. sartenaeri. These species show a decrease in the number of lenses, which is a more widespread and recurring trend in many Phacopinae. [9]

Fossils of Phacops salteri have been found in the trilobite-rich Late Emsian to Early Givetian Floresta Formation of the Altiplano Cundiboyacense, Colombia. [10]

Species

Phacops currently contains the following species:

  • P. accipitrinus(Phillips, 1841) [11]
  • P. algericusAlberti, 1983
  • P. brevicepsBarrande, 1846
  • P. chlupaciAlberti, 1983
  • P. circumspectansPaeckelmann, 1913
  • P. degenerBarrande, 1852
  • P. fecundus
  • P. fragosusStruve, 1970 [9]
  • P. granulatus(Munster, 1840) synonyms Calymene granulata, P. posidoniae [12]
  • P. hoseriHawle & Corda, 1847
  • P. iowensisDelo, 1935 [13]
  • P. imitatorStruve, 1970 [9]
  • P. kockeliAlberti, 1968
  • P. latifrons(Bronn, 1825) [9]
  • P. maurulus
  • P. modestusBarrande
  • P. ouarouroutensisCrônier, 2018
  • P. platilegnotor
  • P. salteriKozlowski, 1923
  • P. sartenaeriStruve, 1985 [9]
  • P. soboleviKielan, 1954
  • P. sternbergi
  • P. turcoRichter & Richter
  • P. wedekindiRichter & Richter, 1926 [12]
  • P. zinkeniF.A. Roemer, 1843

Species previously assigned to Phacops

A number of species previously assigned to the genus Phacops have since been transferred to other genera: [1] [14] [15] [16] [17] [18] [19] [20] [21] [22]

Related Research Articles

<span class="mw-page-title-main">Redlichiida</span> Extinct order of trilobites

Redlichiida is an order of trilobites, a group of extinct marine arthropods. Species assigned to the order Redlichiida are among the first trilobites to appear in the fossil record, about halfway during the Lower Cambrian. Due to the difficulty to relate sediments in different areas, there remains some discussion, but among the earliest are Fallotaspis, and Lemdadella, both belonging to this order. The first representatives of the orders Corynexochida and Ptychopariida also appear very early on and may prove to be even earlier than any redlichiid species. In terms of anatomical comparison, the earliest redlichiid species are probably ancestral to all other trilobite orders and share many primitive characters. The last redlichiid trilobites died out before the end of the Middle Cambrian.

<i>Eldredgeops rana</i> Extinct species of trilobite

Eldredgeops rana is a species of trilobite from the middle Devonian period. Their fossils are found chiefly in the northeastern United States, and southwestern Ontario.

<span class="mw-page-title-main">Phacopina</span> Extinct suborder of trilobites

The Phacopina comprise a suborder of the trilobite order Phacopida. Species belonging to the Phacopina lived from the Lower Ordovician (Tremadocian) through the end of the Upper Devonian (Famennian). The one unique feature that distinguishes Phacopina from all other trilobites are the very large, separately set lenses without a common cornea of the compound eye.

<span class="mw-page-title-main">Phacopidae</span> Extinct family of trilobites

Phacopidae is a family of phacopid trilobites that ranges from the Lower Ordovician to the Upper Devonian, with representatives in all paleocontinents.

<i>Paradoxides</i> Extinct genus of trilobites

Paradoxides is a genus of large to very large trilobite found throughout the world during the Middle Cambrian period. One record-breaking specimen of Paradoxides davidis, described by John William Salter in 1863, is 37 cm (15 in). The cephalon was semicircular with free cheeks ending in long, narrow, recurved spines. Eyes were crescent shaped providing an almost 360° view, but only in the horizontal plane. Its elongate thorax was composed of 19–21 segments and adorned with longish, recurved pleural spines. Its pygidium was comparatively small. Paradoxides is a characteristic Middle-Cambrian trilobite of the 'Atlantic' (Avalonian) fauna. Avalonian rocks were deposited near a small continent called Avalonia in the Paleozoic Iapetus Ocean. Avalonian beds are now in a narrow strip along the East Coast of North America, and in Europe.

<i>Calymene</i> Extinct genus of trilobites

Calymene Brongniart, 1822, is a genus of trilobites in the order Phacopida, suborder Calymenina, that are found throughout North America, North Africa, and Europe in primarily Silurian outcrops. Calymene is closely related to Flexicalymene, and both genera are frequently found enrolled. Calymene trilobites are small, typically 2 cm in length. The cephalon is the widest part of the animal and the thorax usually has 13 segments.

<i>Paciphacops</i> Genus of trilobites

Paciphacops is a genus of trilobites within order Phacopida, suborder Phacopina. This genus is found primarily in the United States and Australia and is easily mistaken for the genera Phacops and Kainops, which are also popular among collectors. One major difference between Paciphacops and Phacops is that the central raised area of the headshield extends beyond the headshield's anterior margin. A major difference between Paciphacops and Kainops is the greater number of eye facets in Kainops. The skin of the visual surface in Paciphacops is thickened and bulged compared to the edge of each lens.

<i>Kainops</i> Genus of trilobites

Kainops is a genus of trilobites from the family Phacopidae, order Phacopida. It can be distinguished from Paciphacops by the greater number of facets to the eye. The form of the furrow between the palpebral area and the palpebral lobe also distinguishes Kainops from the genera Paciphacops and Viaphacops.

<i>Ductina</i> Genus of extinct trilobites

Ductina is a genus of extinct, small to average sized, eyeless phacopid trilobite, that lived during the Devonian.

<i>Chotecops</i> Genus of trilobites

Chotecops is a genus of trilobites from the order Phacopida, suborder Phacopina, family Phacopidae. It was initially erected as a subgenus of Phacops but some later authors thought it distinctive enough to raise its status. Species assigned to this genus occur between the Emsian and the Famennian. Chotecops is the most abundant trilobite in the Hunsrück Slate and due to the excellent preservation, often soft tissue such as antennae and legs have been preserved as a thin sheet of pyrite.

<i>Eldredgeops</i> Genus of trilobites

Eldredgeops is a genus of trilobites in the order Phacopida, family Phacopidae, known from the late Middle and earliest Upper Devonian of Morocco and the USA.

<i>Asaphus</i> Extinct genus of trilobites

Asaphus is a genus of trilobites that is known from the Lower and Middle Ordovician of northwestern Europe.

<i>Analox</i> Extinct genus of trilobites

Analox Rasetti, 1966 is a genus of Eodiscinid trilobites belonging to the family Weymouthiidae Kobayashi T. (1943), Order Agnostida It lived during the Botomian stage. It can easily be distinguished from other trilobites by the two furrows that extend forwards and sidewards from the front of the glabella.

<i>Dicerodiscus</i> Extinct genus of trilobites

Dicerodiscus is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the early part of the Botomian stage, in China. Four species have been assigned to it. Dicerodiscus is unique for an eodiscoid in having conspicuous and curved spines that are attached anteriorly, and at their base are directed outward perpendicular to the midline, before gradually bending further backwards.

<i>Morocconites</i>

Morocconites malladoides is an average size trilobite, which lived during the Devonian period, in what is now southern Morocco. This species is assumed to be a close relative of Acastoides. The most conspicuous feature is the very long upcurved frontal medial spine, a bit like an avocet bill. It is the only known species in this genus.

<span class="mw-page-title-main">Holmiidae</span> Family of trilobites

Holmiidae is a family of trilobites, that lived during the Lower Cambrian (Atdabanian). The Holmiidae is a diverse family of eight genera containing at least 17 species. It includes some of the earliest trilobites of Baltica. Holmiidae occur throughout Baltica and Western Laurentia, and also in Morocco.

<i>Conocoryphe</i> Genus of trilobites

Conocoryphe is a genus of primarily eyeless trilobites belonging to the family Conocoryphidae. They lived during the Middle Cambrian period, about 505 million years ago. These arthropods lived on the sea bottom (epifaunal) and lived off dead particulate organic matter.

<i>Phacops fecundus</i> Species of trilobite

Phacops fecundus is a species of trilobite from the lower Devonian period. Their fossils are found in the Czech Republic.

<i>Galbagnostus</i> Extinct genus of trilobites

Galbagnostus is an extinct genus of agnostid trilobite. It lived during the Lower and Middle Ordovician.

<i>Psychopyge</i> Extinct genus of trilobites

Psychopyge is a genus of trilobite, that lived during the upper Emsian and has been found in Germany and Morocco. It is characterized by the swordlike extension from the front of the head.

References

  1. 1 2 Moore, R.C. (1959). Arthropoda I - Arthropoda General Features, Proarthropoda, Euarthropoda General Features, Trilobitomorpha. Treatise on Invertebrate Paleontology. Vol. Part O. Boulder, Colorado/Lawrence, Kansas: Geological Society of America & University of Kansas Press. pp. 1–560. ISBN   978-0-8137-3015-8.
  2. ↑ Ivo Chlupáč (1973). "The distribution of phacopid trilobites in space and time" (PDF). Fossils and Strata. 4: 399–408.
  3. ↑ Phacops at Fossilworks.org
  4. 1 2 David L. Bruton & Winfried Haas (2001). Philip D. Lane, Derek J. Siveter & Richard A. Fortey (ed.). Trilobites and their Relatives: Contributions from the Third International Conference, Making Phacops come alive. Special Papers in Palaeontology. Vol. 70. Oxford: Wiley-Blackwell. pp. 331–348. ISBN   978-0-901702-81-4.
  5. ↑ Linliang Yuan; Liwen Xiang (1997). "Trilobite Fauna at the Devonian-Carboniferous boundary in South China (S-Guizhou and N-Guangxi)" (PDF). Special Publication of the National Museum of Natural Science. 8.
  6. ↑ George C. Esker III (1968). "Color Markings in Phacops and Greenops from the Devonian of New York". Palaeontology . II (4): 498–499.
  7. ↑ Chlupac, I. (1975). "The distribution of phacopid trilobites in space and time". Evolution and morphology of the Trilobita, Trilobitoidea and Merostomata. Vol. 4. pp. 399–408. doi:10.18261/8200049639-1975-26. ISBN   8 2-00-04963-9.{{cite book}}: |journal= ignored (help)
  8. ↑ Gerry, K. (9 June 2014). "Phacops vs. Eldredgeops". The Fossil Forum.
  9. 1 2 3 4 5 Viersen, van, A.P. (2004). "De mythe van Phacops latifrons[The Myth of Phacops latifrons]". Grondboor & Hamer. 3/4: 66–68.
  10. ↑ Floresta Fauna at Fossilworks.org
  11. ↑ Global Names Index. "Repository "Index to Organism Names"" . Retrieved 4 November 2013.
  12. 1 2 Osmolska, H. (1953). "Famennian Phacopidae from the Holy Cross Mountains (Poland)" (PDF). Acta Palaeontologica Polonica. 3 (2).
  13. ↑ Eldredge, N. (1972). "Systematics and evolution of Phacops rana (Green, 1832) and Phacops iowensis Delo, 1935 (Trilobita) from the Middle Devonian of North America". Bulletin of the American Museum of Natural History. 147 (article 2): 45–114. hdl:2246/1095.
  14. ↑ Shergold, J.H. (1966). "A revision of Acaste downingiae (Murchison) and related trilobites" (PDF). Palaeontology . 9 (2): 183–207. Archived from the original (PDF) on 2011-07-16.
  15. ↑ Crônier, C. (2003). "Systematic relationships of the blind phacopine trilobite Trimerocephalus, with a new species from Causses−et−Veyran, Montagne Noire" (PDF). Acta Palaeontologica Polonica. 48 (1): 55–70. Retrieved 4 November 2013.
  16. ↑ "Acuticeps Kayser, 1889". Global Names Index. Retrieved 23 December 2013.
  17. ↑ Ramskjöld, L.; Werdelin, L. (1991). "The phylogeny and evolution of some phacopid trilobites". Cladistics. 7: 29–74. doi: 10.1111/j.1096-0031.1991.tb00021.x . S2CID   85076301.
  18. ↑ Corbacho, Joan (2011). "Trilobites from the Upper Ordovician of Bou Nemrou - El Kaid Errami (Morocco) [Trilobitas del Ordovícico Superior de Bou Nemrou - El Kaid Errami (Marruecos)]" (PDF). Batelleria. 16: 16–31. Archived from the original (PDF) on 2014-12-20.
  19. ↑ Hansen, George P. (2009). Trilobites of Black Cat Mountain. iUniverse.
  20. ↑ Andrew McRae. "Trilobites in Murchison's "Siluria"".
  21. ↑ Crônier, Catherine; Feist, Raimond (2000). "Evolution et systématique du groupe Cryphops (Phacopinae, Trilobita) du Dévonien Supérieur" [Evolution and systematics of the Cryphops group (Phacopinae, Trilobita) from the Late Devonian]. Senckenbergiana Lethaea. 79 (2): 501–515. doi:10.1007/bf03043651. S2CID   131283519.
  22. ↑ Schoenemann, Brigitte; Clarkson, Euan N.K. (2013). "Discovery of some 400 million year-old sensory structures in the compound eyes of trilobites". Scientific Reports. 3 (1429): 1429. Bibcode:2013NatSR...3E1429S. doi:10.1038/srep01429. PMC   3596982 . PMID   23492459.
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