Aeschronectida is an extinct
order
Order, ORDER or Orders may refer to:
* A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica
* Categorization, the process in which ideas and objects are recognized, differentiated, and understood
...
of
mantis shrimp
Mantis shrimp are carnivorous marine crustaceans of the order Stomatopoda (). Stomatopods branched off from other members of the class Malacostraca around 400 million years ago, with more than 520 extant species of mantis shrimp known. All li ...
-like
crustacean
Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...
s which lived in the
Mississippian subperiod in what is now Montana.
They exclusively lived in the
Carboniferous
The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...
, or the age of amphibians. They have been found mostly in the U.S. and in the British Isles, in 1979 species were found in the
Madera Formation in New Mexico. Aeschronectida was first identified appearing in Continental Europe in around 2014. While sharing similar characteristics to
Stomatopoda, they lack certain physical characteristics of that taxon. The first species of Aeschronectida is accredited to Frederick R. Schram. They diverge substantially from typical
hoplocaridan morphology by having more unmodified thoracopods.
It's theorized that these thoracopods evolved to become more specialized, making them potential ancestors to
Stomatopoda.
Morphology
Aeschronectida have typical characteristics of hoplocarids including 3-flagellate first antenna, an enlarged abdomen, a shortened thorax, 3-segmented thoracic protopods, cephalic kinesis, pleopodal epipodite gills, and an articulated rostrum. The bodies of Aeschronectids are divided into four tagmata: the food-processing unit, the pleon plus tailfan, the walking-appendage area, and the sensorial unit. They differ from typical hoplocarids by having their carapace covering the entire thorax and the unspecialized thoracopods acting as natatory appendages
Like the Mantis Shrimp, their eyes are stalked and elevated on the anterior cephalon. Unlike Stomatopods, their functional morphology is poorly understood. This limited understanding of their morphology and the presence of damaged fossils makes them much more difficult to not only identify, but to specify species as well.
Taxonomy
Class:
Malacostraca
Malacostraca is the second largest of the six classes of pancrustaceans behind insects, containing about 40,000 living species, divided among 16 orders. Its members, the malacostracans, display a great diversity of body forms and include crab ...
Subclass:
Hoplocarida
Families & Genera
*
Aenigmacarididae
**
Aenigmacaris
*** ''Aenigmacaris minima''
*** ''Aenigmacaris cornigerum''
**
Joanellia
*** Joanellia lundi
*** Joanellia elegans
* Aratidecthidae
**
Aratidecthes
*** aratidecthes johnsoni
**
Crangopsis
* Kallidecthidae
**
Kallidecthes
*** Kallidecthes richardsoni
Identification/Studies
Aeschronectids are particularly hard to identify due to their fossils being damaged or half-digested. A preserved structure of a tail fan and attached abdomens are generally used to distinguish Aeschronectids from their modern counterparts. Due to the damage many fossils have sustained, many of them are identified as being part of Aeschronectida and not distinguished to a singular species of genus. Many studies involving Aeschronectids generally try and distinguish new families and Genera or try and connect them as potential predecessors to Stomatopoda.
[Smith, C. P., Aubier, P. A. U. L., Charbonnier, S. Y. L. V. A. I. N., Laville, T. H. O. M. A. S., Olivier, N. I. C. O. L. A. S., Escarguel, G. I. L. L. E. S., ... & Brayard, A. (2023). Closing a major gap in mantis shrimp evolution-first fossils of Stomatopoda from the Triassic. ''Bulletin of Geosciences'', ''98''(1), 95-110.]
References
{{Taxonbar, from=Q4688535
Prehistoric Malacostraca
Crustacean orders
Prehistoric arthropod orders
Mississippian first appearances