Lejopyge laevigata

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Lejopyge laevigata
Temporal range: Guzhangian–Paibian
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Lejopyge laevigata.jpg
Illustration of Lejopyge laevigata [1]
Lejopyge laevigata pygidium.jpg
Lejopyge laevigata pygidium
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Arthropoda
Class:† Trilobita
Order:† Agnostida
Family:† Ptychagnostidae
Genus:† Lejopyge
Species:
†L. laevigata
Binomial name
†Lejopyge laevigata
(Dalman, 1828)
Synonyms
  • Agnostus laevigatus(Dalman, 1828)
  • Battus laevigatusDalman, 1828

Lejopyge laevigata is a species of agnostid trilobite belonging to the genus Lejopyge . It existed during the Guzhangian to the Paibian Age (around 500.5 to 497 million years ago) of the Cambrian. It has a cosmopolitan distribution and is an important index fossil in biostratigraphy.

Contents

Description

Lejopyge laevigata exhibits a cephalon and pygidium that are smooth and almost featureless (effaced). Both possess axial furrows that gradually become shallower until they disappear distally. They surround the rear edges of the glabella (reaching about as far or a little past the basal glabellar lobes) and the anterior end of the central lobe of the pygidium. Basal furrows are also present. The genae ("cheeks") are usually smooth, but in extremely rare cases they may possess small pits (scrobicules) of moderate depth. The border around the pygidium is uniform in width at the back and narrows towards the front. [2] [3] [4] [5] Like all members of the suborder Agnostina, Lejopyge laevigata is completely blind. [6]

Distribution

Lejopyge laevigata has a cosmopolitan distribution, making it an ideal intercontinental correlation tool in biostratigraphy. It has been described from Argentina, Australia (including Tasmania), China, Denmark (including Greenland), Germany, India, Kazakhstan, Norway, Poland, Turkestan, Uzbekistan, Russia, Sweden, the United Kingdom, and the United States (including rare finds in Alaska). [4] [7]

Taxonomy

Lejopyge laevigata is classified under the genus Lejopyge of the family Ptychagnostidae. [2] It was originally described in 1828 by the Swedish naturalist Johan Wilhelm Dalman as Battus laevigatus. In a monograph on Bohemian trilobites, Prodrom einer Monographie der böhmischen Trilobiten (1847), the Czech fossil collector Ignaz Hawle and botanist August Carl Joseph Corda established the genus Lejopyge using B. laevigatus as the type species. [8] [9]

Lejopyge armata was formerly classified as a subspecies of Lejopyge laevigata. The former differs from the latter in having spines on both the cephalon and the pygidium, a characteristic unique to the entire genus. They are sometimes found together, but most collections are uniformly composed of either of them, which rules out sexual dimorphism as an explanation for the differences. Due to this, the American paleontologist Richard A. Robison separated Lejopyge armata from Lejopyge laevigata in 1984. [2] [4] [10]

Biostratigraphy

Lejopyge laevigata is used in biostratigraphy as an index fossil. Its first appearance at the GSSP section of the Huaqiao Formation in Hunan, China is defined as the beginning of the Guzhangian Age (around 500.5 million years ago) of the Miaolingian (Middle Cambrian). It has also been used as a zonal guide in various fossil localities around the world. [4] [7]

Related Research Articles

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

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<i>Phalagnostus</i>

Phalagnostus is a genus of small trilobites, in the order Agnostida. It lived during the Middle Cambrian, in what are now Canada, China, the Czech Republic, Denmark, England, France, the Russian Federation, Wales, Sweden, and possibly the United States (Vermont). The headshield is almost entirely effaced and wider than the tailshield. The pygidium is also very effaced, but the ovate pygidial axis is well defined and a border furrow is also present.

The Guzhangian is an uppermost stage of the Miaolingian Series of the Cambrian. It follows the Drumian Stage and precedes the Paibian Stage of the Furongian Series. The base is defined as the first appearance of the trilobite Lejopyge laevigata around 500.5 million years ago. The Guzhangian-Paibian boundary is marked by the first appearance of the trilobite Glyptagnostus reticulatus around 497 million years ago.

Ptychagnostidae Extinct family of trilobites

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Condylopygidae

The Condylopygidae Raymond (2013) are a family of small trilobites that lived during the Middle Cambrian, and found in Canada, the Czech Republic, Germany, France, Spain, England, Wales, Sweden, and the Russian Federation (Siberia). They uniquely differ from all other Agnostina in having the frontal glabellar lobe wider than the rear lobe. The Condylopygidae are the only family assigned to the Condylopygoidea superfamily.

Diplorrhina Hawle and Corda (1847) is a genus of trilobite belonging to Order Agnostida. It lived during the early Middle Cambrian in what are now the Czech Republic and the North Siberian plateau. as in members of the family Peronopsidae it lacks a preglabellar furrow. Both cephalon and pygidium lack spines. It is difficult to distinguish Diplorrhina from many other peronopsids.

<i>Toragnostus</i>

Toragnostus is a genus of trilobites restricted to the late Middle Cambrian. Its remains have been found in the United States, Greenland, Denmark, China, Sweden, the Russian Federation, and Kazakhstan. Its headshield and tailshield are almost completely effaced and it has two thorax segments.

Schmalenseeia is genus of trilobites of uncertain affinity, that lived during the middle Middle to earliest Upper Cambrian. Species assigned to Schmalenseeia have been found in Norway, Sweden, Northern Siberia, Eastern China, Australia (Tasmania), India (Himalayas) and the United Kingdom.

<i>Tricrepicephalus</i>

Tricrepicephalus is an extinct genus of ptychopariid trilobites of the family Tricrepicephalidae with species of average size. Its species lived from 501 to 490 million years ago during the Dresbachian faunal stage of the late Cambrian Period. Fossils of Tricrepicephalus are widespread in Late Cambrian deposits in North America, but is also known from one location in South-America. Tricrepicephalus has an inverted egg-shaped exoskeleton, with three characteristic pits in the fold that parallels the margin of the headshield just in front of the central raised area. The articulating middle part of the body has 12 segments and the tailshield carries two long, tubular, curved pygidial spines that are reminiscent of earwig's pincers that rise backwards from the plain of the body at approximately 30°.

References

  1. ↑ Nils Peter Angelin (1851–1878). Gustaf Lindström (ed.). Palæontologica Scandinavica, Pars I: Crustacea Formationis Transitionis. Holmiæ. pp. 8, pl.6, f.10.
  2. 1 2 3 Richard A. Robison (1984). "Cambrian trilobites of east-central Alaska". Cambrian Agnostida of North America and Greenland: Part I: Ptychagnostidae. The University of Kansas Paleontological Contributions: Paper 109. Paleontological Institute, University of Kansas. pp. 1–60. ISSN   0075-5052.
  3. ↑ Brian Daily; James B. Jago (1975). "The Trilobite Lejopyge Hawle and Corda and the middle-upper Cambrian boundary" (PDF). Palaeontology. 18 (3): 527–550.[ permanent dead link ]
  4. 1 2 3 4 Anders Bengtsson (1999). "Trilobites and bradoriid arthropods from the Middle and Upper Cambrian at Gudhem in Västergötland, Sweden". Examensarbete I Geologi Vid Lunds Universitet, Historisk Geologi och Paleontologi (106): 1–21.
  5. ↑ Allison R. Palmer (1968). "Cambrian trilobites of east-central Alaska". Lower paleozoic paleontology and stratigraphy, east-central Alaska. Geological Survey Professional paper 559-B. United States Geological Survey, US Department of the Interior, United States Government Printing Office. p. B28.
  6. ↑ Samuel M. Gon III. "Agnostida Fact Sheet". A Guide to the Orders of Trilobites. Retrieved 18 November 2012.
  7. 1 2 Shanchi Peng; Loren E. Babcock; Jingxun Zuo; Huanling Lin; Xuejian Zhu; Xianfeng Yang; Richard A. Robison; Yuping Qi; Gabriella Bagnoli; Yong'an Chen (2009). "The Global Boundary Stratotype Section and Point (GSSP) of the Guzhangian S tage (Cambrian) in the Wuling Mountains, Northwestern Hunan, China". Episodes. 32 (1): 41–56. doi: 10.18814/epiiugs/2009/v32i1/006 .
  8. ↑ "Lejopyge laevigata". Paleobiology Database. Retrieved 16 November 2012.
  9. ↑ Oldřich Fatka; Petr Budil (2012). "Foreword". In Petr Budil; Oldřich Fatka (eds.). The 5th Conference on Trilobites and their relatives, 1st – 4th July 2012, Prague, Czech Republic. Česká geologická služba. p. 5. ISBN   9788070757871.
  10. ↑ Richard A. Robison (1988). "Trilobites of the Holm Dal Formation (late Middle Cambrian), central North Greenland". Meddelelser om Grønland. Geoscience. 20: 23–103. ISBN   9788763511902.
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