Siphonotretida

Siphonotretida Temporal range: Cambrian Stage 4–Ludlow PreꞒ Ꞓ O S D C P T J K Pg N
Upper Ordovician of Oklahoma
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Brachiopoda
Class:	Lingulata
Order:	†Siphonotretida Kuhn, 1949
Superfamily:	†Siphonotretoidea Kutorga, 1848
Family:	†Siphonotretidae Kutorga, 1848

Siphonotretida is an extinct order of linguliform brachiopods in the class Lingulata. The order is equivalent to the sole superfamily Siphonotretoidea, itself containing the sole family Siphonotretidae. Siphonotretoids were originally named as a superfamily of Acrotretida, before being raised to their own order.^[1]

Evolution

Spihonotretids were most abundant in the

Siphonotretids had simple, rounded shells, with an ornamentation of hollow spines[1] or rarely pointed tubercles.^[3] The shell is usually ventribiconvex (both valves convex, the ventral valve moreso) and composed of microscopic granules of apatite. The inner surface of the shell tends to be weakly mineralized, so many aspects of the musculature and other soft anatomy are difficult to estimate in most species. Available data supports comparison to the internal structures of lingulids.^[1] Siphonotretids may be related to the linguloid families Lingulellotretidae or Dysoristidae.^[8]

Similar to acrotretides, the pedicle foramen was set at the apex of the ventral valve, though it is often elongated into a tubular groove opening forwards. This groove lies on a triangular extension of the ventral valve, known as a pseudointerarea, which overhangs the dorsal valve. Unlike acrotretides, the adult shell is spinose while the larval shell lacks a pitted texture.^[1]

The possible siphonotretid

List of genera

• Ashgill
  ")
• Acanthotretella? Holmer & Caron, 2006^[9] (mid-Cambrian, "Stage 4" to Miaolingian; provisionally assigned to Siphonotretoidea)^[2]
• Caradoc
  ")
• Collarotrella^[3] Mergl, 1997 (Ordovician, "Arenig")
• Celdobolus Havlíček, 1982 (Ordovician, "Arenig")
• Cyrbasiotreta Williams & Curry, 1985 (Middle Ordovician, "Arenig")
• Llanvirn
  ")
• Gorchakovia Popov & Khazanovitch (in Popov et al., 1989) (Upper Cambrian)
• Helmersenia Pander (in von Helmersen, 1861) (Upper Cambrian to Ordovician)
• Karnotreta Williams & Curry, 1985 (Middle Ordovician, "Arenig")
• Mesotreta Kutorga, 1848 (Lower to Middle Ordovician, "Arenig")
• Multispinula Rowell, 1962 (Middle to Upper Ordovician, "Arenig" to "Ashgill")
• Nushbiella Popov (in Kolobova & Popov, 1986) (Middle to Upper Ordovician, "Arenig" to "Caradoc")
• Oaxaquiatreta Streng, Mellbin, Landing & Keppie, 2011^[11] (Upper Cambrian to Tremadocian)
• Orbaspina^[3] Valentine & Brock, 2003^[8] (Silurian, late Llandovery to Ludlow)^[4]
• Quasithambonia? Bednarczyk & Biernat, 1978 (Ordovician, "Arenig")
• Schizambon Walcott, 1884 (Middle Cambrian to Ordovician, "Arenig")
• Siphonobolus Havlíček, 1982 (Ordovician, "Tremadoc" to "Arenig")
• Siphonotreta
  de Verneuil, 1845 (Ordovician, "Arenig" to "Caradoc")
• Siphonotretella Popov & Holmer, 1994 (Lower Ordovician, "Tremadoc" to "Arenig")

References

1. ^
   ISBN 0-8137-3108-9
   .
2. ^
   S2CID 59439966
   .
3. ^
   ISBN 978-0-8137-3136-0
   .
4. ^ ^{a b} Mergl, M. (2003). "Orbaspina chlupaci sp. nov., a new siphonotretid brachiopod from the Silurian of the Barrandian area, Bohemia" (PDF). Bulletin of Geosciences. 78 (4): 419–421.
5. doi:10.3140/bull.geosci.1710
   .
6. ISSN 1342-937X
   .
7. ISSN 0435-4052
   .
8. ^
   doi:10.3853/j.0067-1975.55.2003.1378
   .
9. ^
   doi:10.1111/j.1463-6395.2006.00241.x
   .
10. ^ "Acanthotretella spinosa". Burgess Shale Fossil Gallery. Virtual Museum of Canada. 2011. Archived from the original on 2020-11-12.
11. doi:10.1666/10-074.1
    .

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