Endocerida

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Endocerida
Endoceras fossil shells with soft tissue outline reconstruction

Endoceras fossil shells with soft tissue outline reconstruction
Temporal occurrence
Lower Ordovician to Middle Silurian
485.4 to 430 million years
Locations
  • Worldwide
Systematics
Primordial mouths (protostomia)
Lophotrochozoa (Lophotrochozoa)
Molluscs (mollusca)
Cephalopods (cephalopoda)
Nautiloids (Nautiloidea)
Endocerida
Scientific name
Endocerida
Hyatt in Zittel , 1900

The Endocerida are an extinct order of the cephalopods (Cephalopoda), which belongs to the nautiloids and is related to the recent pearl boats (Nautilidae). The oldest fossil records come from the marine sediments of the beginning Ordovician 485.4 million years ago, the youngest from the middle Silurian ( Wenlock ) approx. 430 million years ago. The largest Endocerida such as Cameroceras reached a total length of up to 10 meters (of which up to 9 meters housing ).

features

The Endocerida usually have large, elongated and chambered housing with a siphon cord at the edge . Characteristic elements of the Endocerida are cone-shaped intrasiphonal deposits with the tip pointing backwards, which gradually fill the rear part of the siphon cord massively. These consist primarily of aragonite (calcium carbonate) and to a lesser extent organic deposits. The function of this backfill is to trim the body so that the center of gravity of the housing (including the animal in the living chamber) shifts to the center of the body. Because if there was no ballast in the rear part of the housing, the center of gravity would be in the front part of the housing due to the weight of the soft body and the phragmocone would stand vertically upwards. Fast horizontal movement in the water would be difficult. The buoyancy generated by the housing was sufficient to keep the entire body "floating" in the water. An ascent or descent in the body of water by changing the buoyancy in the housing, as with the pearl boats, was probably not possible. The locomotion takes place presumably exclusively with the help of the funnel (hyponome) and the recoil principle .

ecology

Like the rest of the cephalopods, the Endocerida lived in the sea. They likely fed on fish , trilobites, and arthropods (e.g. sea ​​scorpions ). They would then have been among the top predators in the Ordovician seas. In mid-2018, the theory was published that the larger Endocerida could have been filter feeders , similar to today's baleen whales . According to this theory, there would have been skins between the tentacles, as is also present in the recent vampire squid ( Vampyroteuthis infernalis ).

Systematics

In the classic systematic classification of cephalopods into nautiloids , ammonites and squids, the Endocerida are placed in the subclass of nautiloids. In other classifications (Shevyrev 2006) it is combined with two other orders ( Yanhecerida and possibly also the Intejocerida ) to the parent (or subclass ) Endoceratoidea within the cephalopods. Also in the phylogenetic systematics with the division in palcephalopoda and neocephalopoda the endocerida can be merged with the Yanhecerida and Intejocerida as Endoceratoidea. They are basal at the root of the cephalopods. There are also proposals to subdivide the order Endocerida into two or three suborders. So far, these proposals have not been successful.

Over 20 families with around 80 genera are currently being put into order:

literature

  • Andrew H. King: Mollusca: Cephalopoda (Nautiloidea). In: Michael J. Benton (ed.): The fossil record 2. Chapman & Hall, London et al. 1993, ISBN 0-412-39380-8 , pp. 169-188.
  • Aleksandr A. Shevyrev: The cephalopod macrosystem: A historical review, the present state of knowledge, and unsolved problems: 2. Classification of nautiloid cephalopods. In: Paleontological Journal. Vol. 40, No. 1, 2006, ISSN  0031-0301 , pp. 46-54, doi : 10.1134 / S0031030106010059 .
  • Curt Teichert : Endoceratoidea. In: Curt Teichert, Bernhard Kummel , Walter C. Sweet, HB Stenzel, William M. Furnish, Brian F. Glenister, Heinrich K. Erben , Raymond Cecil Moore , DEN Zeller (eds.): Treatise on Invertebrate Paleontology. Part K: Mollusca. 3: Cephalopoda - General Features Endoceratoidea - Actinoceratoidea - Nautiloidea - Bactritoidea. Geological Society of America et al., New York NY et al. 1964, K160-K189.

Individual evidence

  1. ↑ a b c Sreepat Jain (2016): Fundamentals of Invertebrate Palaeontology: Macrofossils . P. 80. Springer. ISBN 978-81-322-3656-6
  2. ↑ Aleksandr A. Mironenko. 2018. Endocerids: Suspension Feeding Nautiloids? Historical Biology: An International Journal of Paleobiology. DOI: 10.1080 / 08912963.2018.1491565

Web links

Commons : Endocerida  - collection of images, videos and audio files