Acrotretida

from Wikipedia, the free encyclopedia
Acrotretida
Prototreta trapeze

Prototreta trapeze

Temporal occurrence
Cambrian to Devonian
approx. 540 to 360 million years
Locations

worldwide

Systematics
Primordial mouths (protostomia)
Lophotrochozoa (Lophotrochozoa)
Arm pods (Brachiopoda)
Linguliformea
Lingulata
Acrotretida
Scientific name
Acrotretida
Kuhn , 1949

The acrotretida are an extinct order of brachiopods from the sub-tribe of Linguliformea .

features

Inner and outer shell features using the example of Eohadrotreta zhenbaensis . From Zhang et al., 2018

Unless otherwise stated, the description is based on Holmer & Popov , 2000. Letters and abbreviations in quotation marks refer to the sketches of Eohadrotreta zhenbaensis in the figure below.

External shape of the shells and internal structure

The Acrotretida are an order of small to tiny, lockless ("inarticulate") brachiopods. The shell diameters are usually in the order of 1–2 mm. Only a few forms reach shell diameters of 5 mm or less. Both the dorsal ("C", "D") and the ventral valve ("A", "B") are curved outwards (biconvex), whereby the curvature of the ventral valve (pedicle valve) is usually more pronounced (ventribiconvex ). In most cases the curvature of the ventral valve is so pronounced that it takes on a bag-like, conical to sub-conical shape. The shells of the larval stages ("ms") are relatively small with a diameter of <0.3 mm and have characteristic micro-ornamentation consisting of numerous circular pits. In the related lingulida , the shell diameter of the larvae is usually> 0.3 mm

The stem hole (foramen - "f") is apical , at the tip of the conical ventral valve.

As with all representatives of the linguliformea, the shell was organophosphatic, that is, it consisted of fluoroapatite in an organic matrix of glycosaminoglycans , β-chitin and proteins . The fine structure of the bowls is described as "columnar"; individual apatite lamellae, separated from one another by the organic matrix, are connected to one another by apatite "columns" standing vertically between the lamellae. The columns have a diameter of 1.5–5 μm and are traversed by a thin channel along the longitudinal axis, so that a tiny pore is formed that can pass through several layers of the shell. This shell structure seems to be typical of representatives of the acrotretidea, but does not occur exclusively within this order. The shell structure of the acrotretida thus differs significantly from that of most of the other representatives of the linguliformea, in which the apatite pillars between the lamellae are not perpendicular, but alternately at an angle to them, thus forming an approximately X-shaped pattern ("baculate shell structure") . The only exception to this rule seems to be the representatives of the Curticiidae within the Acrotretida. In this family, the shell is made up of both columnar and baculate structural areas.

Inner shell features

There is no hinge-like connection (“lock”) between the two valves, as is the case with all representatives of the linguliformea . The two shell flaps were only held together by the muscles of the soft body. The muscle system of the acrotretida differs markedly from that of other representatives of the linguliformea. In the ventral valve there is a pair of main muscle attachment points ("ventral cardinal scars" - "c") on the posterior side of the shell. Another prominent muscle attachment point is an extension ("apical process" - "a") near the tip of the ventral valve immediately in front of the stem hole ("f").

The dorsal valve (arm valve) usually has a triangular median septum (“s”) on the inside (“C”). The paired main muscle attachment points ("c") are close to the pseudo-interarea ("p").

Temporal and geographical distribution

The earliest representatives of the Acrotretida appear relatively late in the officially still nameless "Stage 3" ( "2nd series" of the Cambrian). "Level 3" essentially corresponds to the Atdabanium of the regional chronostratigraphic classification of Siberia and in the specialist literature the late Atdabanium is often given informally as the earliest occurrence of the Acrotretida. Eohadrotreta from the Shuijingtuo formation in the Chinese province of Shaanxi is one of the earliest representatives of the order .

These early Acrotretida of the Cambrian can usually be assigned to the families of the Acrotretidae or the Ceratretidae. Most of the other families only appear from the uppermost Cambrian or the lower Ordovician. Two families, the Ceratretidae and the Curticiidae, were extinct again by the end of the Cambrian. In the second half of the Cambrian, however, the order provided the most important group of brachiopods with numerous genera occurring worldwide.

Two other families, the Ephippelasmatidae and the Eoconulidae, fell victim to the Ordovician mass extinction during the Andean-Sahara Ice Age towards the end of the Ordovician ( Hirnantium ). Only the families of the Acrotretidae, Scaphelasmatidae, Torynelasmatidae and Biernatidae survived the global crisis as Lazarus taxa with a greatly reduced number of species and genera. Only the Biernatidae can be detected in the middle, possibly even in the Upper Devonian.

Systematics

 Brachiopoda  
  Linguliformea  
  Paterinata  

 Paterinida  †


  Lingulata  


 Acrotretida  †


   

 Siphonotretida  †



   

 Lingulida




  Craniiformea  

 Craniida 


   

 Craniopsida  †


   

 Tomerellida  †


Template: Klade / Maintenance / 3

 Rhynchonelliformea  
  Chileata  

 Chileida  †


   

 Dictyonellidina  †



  Obolellata  

 Obolellida  †


  Kutorginata  

 Kutorginida  †


  Strophomenata  


 Orthotetidina  †


   

 Triplesiidina  †



   

 Billingselloidea  †


   

 Clitambonitidina  †


   

 Strophomenida  †


   

 Productida  †




Template: Klade / Maintenance / 3

  Rhynchonellata  

 Protorthida  †


   

 Orthida  †


   

 Pentamerida  †


   

 Rhynchonellida


   


 Spiriferida  †


   

 Thecideidina



   

 Atrypida  †


   

 Athyridida  †


   

 Terebratulida



Template: Klade / Maintenance / 3



Template: Klade / Maintenance / 3

Template: Klade / Maintenance / 3Template: Klade / Maintenance / 4Template: Klade / Maintenance / 5

Template: Klade / Maintenance / 3

Template: Klade / Maintenance / Style
Systematic position of the acrotretida within the pods according to Williams et al., 1996;

The system presented here follows, unless otherwise stated, the Treatise on Invertebrate Paleontology or the work of Alwyn Williams et al. , 1996.

External system

The Acrotretida form together with the also extinct Siphonotretida and the Lingulida, to which the recent genus Lingula also belongs, the class of the Lingulata . Together with the extinct class of Paterinata the lingulata form the subtype of Linguliformea which within the Brachiopoda the Craniiformea and Rhynchonelliformea faces.

Internal system

The order of the Acrotretida includes only one superfamily (Acrotretoidea) from 8 families with a total of at least 76 genera. There are also three other genera incertae sedis . For reasons of clarity, only the subordinate taxa of the type genus Acrotreta and the type species Acrotreta subconica are listed here.

The assignment of the Curticiidae to the Acrotretida was later questioned, especially because of the different shell structure.

Paleecology

The Acrotretida were, like all representatives of the arm pods, filter feeders , which lived largely sessile after a planktonic larval stage . Because of the small shell size of usually only a few millimeters, Michael G. Bassett , 1984, suspects a life in the sand gap system for the adult animals, similar to the recent genus Gwynia , which is not closely related to the Acrotretida.

Michal Mergl and Stanislava Vodrážková discuss three possible ways of life in 2012 using the example of the genus Opsiconidion from the Lower to Middle Devonian of the Prague Mulde ; as a semi- infauna, half buried in the fine-grained sediment, in the sand gap system of coarser-grained sediments or as an epiplankton attached to seaweed floating in the water. The two authors prefer the latter interpretation, but also emphasize that there is no direct fossil evidence for this.

Finds from the Chengjiang Faunal Community show acrotretids of the species Kuangshanotreta malungensis, however, as epizoa (" perch animals ") on the tang-shaped alga Malongitubus kuangshanensis . A similar finding is available for Acrothyra gregaria from the Burgess schists in connection with the coeloscleritophore Chancelloria eros or the horned siliceous sponge Pirania muricata , and in 2005 Holmer et al. from the Lower Ordovician of Utah a mass accumulation of Ottenbyella ibexiana associated with a concentration of sponge needles , possibly suggesting a similar paleecological relationship.

However, it is also possible that different representatives of the acrotretida have adapted to different lifestyles.

Individual evidence

  1. ^ O. Kuhn: Textbook of Palaeozoology. 326 S., E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, 1949
  2. ↑ Z. Zhang, Z. Zhang, LE Holmer & F. Chen: Post ‐ metamorphic allometry in the earliest acrotretoid brachiopods from the lower Cambrian (Series 2) of South China, and its implications In: Palaeontology , Vol. 61, Issue 2 , Pp. 183-207, 2018. doi : 10.1111 / pala.12333
  3. ↑ a b c d e f g L. E. Holmer & LE Popov: Lingulata. In: A. Williams, SJ Carlson, CHC Brunton, LE Holmer, LE Popov, M. Mergl, JR Laurie, MG Bassett, LRM Cocks, R. Jia-Yu, SS Lazarev, RE Grant, PR Racheboeuf, J. Yu- Gan, BR Wardlaw, DAT Harper, AD Wright & M. Rubel: Brachiopoda - Linguliformea, Craniiformea, and Rhynchonelliformea ​​(part) , Treatise on Invertebrate Paleontology, Part H, Vol. 2 & 3, pp. 30–157, 2000
  4. ↑ a b G. T. Ushatinskaya: Stratigraphic and Geographic Distribution of Acrotretids (brachiopods, lingulata) in the Middle and Late Cambrian. In: Paleontological Journal , Vol. 44, No. 9, pp. 1164–1175, 2010. (abstract)
  5. ↑ a b L. E. Holmer: Middle Ordovician phosphatic inarticulate brachiopods from Våstergotland and Dalarna, Sweden. In: Fossils and Strata , Vol. 26, 172 S., 1989. (digitized version)
  6. ↑ LE Holmer, L. Popov & M. Streng: Organophosphatic stem group brachiopods: implications for the phylogeny of the subphylum Linguliformea. In: Fossils and Strata , Vol. 54, pp. 3–11, 2008. (digitized version)
  7. ↑ M. Streng, LE Holmer, LE Popov & GE Budd: Columnar shell structures in early linguloid brachiopods - new data from the Middle Cambrian of Sweden. In: Earth and Environmental Science Transactions of the Royal Society of Edinburgh , Vol. 98, pp. 221–232, 2008. (digitized version)
  8. ^ A b M. Streng & LE Holmer: Discovery of a new type of shell structure within the organophosphatic brachiopods and the status of the family Curticiidae. In: Geologiska Forengingens I Stockholm Forhandlingar , Vol. 127, pp. 7–16, 2005. (available)
  9. ^ G. Li & LE Holmer: Early Cambrian lingulate brachiopods from the Shaanxi Province, China. In: GFF , Vol. 126, pp. 193–211, 2004. (digitized version)
  10. ↑ J.-Y. Rong, AJ Boucot, DAT Harper, R.-B. Zhan & RB Neuman: Global analyzes of brachiopod faunas through the Ordovician and Silurian transition: reducing the role of the Lazarus effect. In: Canadian Journal of Earth Sciences , Vol. 43, Issue 1, pp. 23-39, 2006. (digitized version )
  11. ↑ M. Mergl: Lingulate Brachiopods of the Silurian and the Devonian of the Barrandian (Bohemia, Czech Republic). In: Acta Musei Nationalis Pragae , Series B, Historia Naturalis, Vol. 57, Issue 1–2, pp. 1–49, 2001. (digitized version )
  12. ^ A b A. Williams, SJ Carlson, CHC Brunton, LE Holmer & L. Popov: A supra-ordinal classification of the Brachiopoda. In: Proceedings of the Royal Society B: Biological Sciences , Vol. 351, pp. 1171-1193, 1996. (digitized version )
  13. ↑ LE Holmer & L. Popov: Revision of the type species of Acrotreta and related Lingulate brachiopods. In: Journal of Paleontology , Vol. 68, Issue 3, pp. 433-450, 1994. (digitized version )
  14. ↑ Ch. Schuchert: A Classification of the Brachiopoda. In: The American Geologist , Vol. XI, No. 3, pp. 141–167, 1893. (digitized version )
  15. ^ AJ Rowell: Inarticulata. In: RC Moore (Ed.): Treatise on Invertebrate Paleontology, Part H, Brachiopoda 1 (2) , H260 – H296, Geological Society of America and University of Kansas Press, 1965.
  16. ↑ Ch. D. Walcott: Cambrian Geology and Paleontology No. 4 - Classification and Terminology of the Cambrian Brachiopoda. In: Smithsonian Miscellaneous Collections , Vol. LIII, No. 1811, pp. 139–165, 1908. (digitized version )
  17. ↑ a b T. P. Topper, Z. Zhang, JC Gutiérrez-Marco & DAT Harper: The dawn of a dynasty: life strategies of Cambrian and Ordovician brachiopods. In: Lethaia , 13 S., 2017. doi : 10.1111 / let.12229 (digitized version )
  18. ↑ M. Mergl & St. Vodrážková: Emsian-Eifelian lingulate brachiopods from the Daleje-Třebotov Formation (Třebotov and Suchomasty limestones) and the Choteč Formation (Choteč and Acanthopyge limestones) from the Prague Basin; the Czech Republic. In: Bulletin of Geosciences , Vol. 87, No. 2, pp. 315–332, 2012 (digitized version )
  19. ^ H. Wang, Z. Zhang, LE Holmer, S. Hu, X. Wang & G. Li: Peduncular attached secondary tiering acrotretoid brachiopods from the Chengjiang fauna: Implications for the ecological expansion of brachiopods during the Cambrian explosion. In: Palaeogeography, Palaeoclimatology, Palaeoecology , Vol. 323-325, pp. 60-67, 2012. (digitized version )
  20. ↑ a b T. P. Topper, LC Strotz, LE Holmer & JB Caron: Survival on a soft seafloor: life strategies of brachiopods from the Cambrian Burgess Shale. In: Earth Science Reviews , Vol. 151, pp. 266–287, 2015. (manuscript version )
  21. ^ LE Holmer, LE Popov, M. Streng & JF Miller: Lower Ordovician (Tremadocian) lingulate brachiopods from the House and Fillmore formations, Ibex Area, western Utah, USA . In: Journal of Paleontology , Vol. 79, Issue 5, pp. 884–906, 2005. (digitized version )

Web links