#thylacocephalan

By @stolpergeist​​

Etymology: Shrimp from the Ankitokazo basin

First Described By: Arduini, 1990

Classification: Biota, Archaea, Proteoarchaeota, Asgardarchaeota, Eukaryota, Neokaryota, Scotokaryota, Opimoda, Podiata, Amorphea, Obazoa, Opisthokonta, Holozoa, Filozoa, Choanozoa, Animalia, Eumetazoa, Parahoxozoa, Bilateria, Nephrozoa, Protostomia, Ecdysozoa, Panarthropoda, Tactopoda, Arthropoda, Pancrustacea, Thylacocephala, Concavicarida, Concavicarididae

Referred Species: A. acutirostris, A. bandoi, A. chaohuensis, A. tatensis

Status: Extinct 

Time and Place: 250 to 247 Ma, in the Olenekian of the Early Triassic.

Ankitokazocaris is known from Madagascar, China, and Japan.

Physical Description: The first thing you might be thinking is “what the hell is that thing?” That, my friends, is a thylacocephalan. Thylacocephala was a clade of arthropods that lived from the Silurian to the Cretaceous. Most of their bodies were protected by a large carapace, which was open at the bottom. At the front of the carapace was an opening for the eyes. Three pairs of legs dangled down from the bottom of the carpace. These legs were not adapted for swimming, but for prey capture.

Ankitokazocaris is an average concavicaridan, growing up to around 4 cm. The carapace had a rather large head opening at the front of the carapace, out of which two large eyes peeked. This opening was protected at the top by an extension of the carapace called the rostrum. Of the three raptorial limb pairs, the last pair was by far the largest. There were also several pairs of shorter legs at the back of the carapace. Unfortunately, a lot of anatomy such as what the gills and mouth looked like are unknown, because the carapace always covers these in the fossils

Diet: It is presumed that thylacocephalans like Ankitokazocaris were predatory. They had front limbs that would have been useful for grabbing small prey floating in the water.

Behavior: Very little is known about thylacocephalan behavior, in part because, well, look at it. As their limbs seem poorly-equipped for swimming vigorously, they probably hung out in the water column, going after any animals and detritus floating by. The large compound eyes would be good for seeing things floating in dim light. It’s possible that they rested on the seafloor during some periods of the day, rising up to catch prey. It’s also possible that Ankitokazocaris lived in small schools for mutual protection; this has been proposed for other thylacocephalans.

Ecosystem: Ankitokazocaris probably lived in relatively shallow pelagic environments. Unfortunately not many other fossils have been found in Ankitokazocaris-bearing deposits, but these include ammonites, bivalves, and in Japan, other thylacocephalans such as Kitakamicaris and Ostenocaris.

Other: There’s still much that is unknown about thylacocephalans, such as many details of their softer anatomy and lifestyle and what their closest relatives are. The current consensus is that they’re probably crustaceans, but to my knowledge this has yet to be confirmed with phylogenetic analysis.

~ By Henry Thomas

Sources under the cut

By @stolpergeist​

Etymology: Shrimp from the Ankitokazo Basin, Madagascar

First Described By: Arduini, 1990

Classification: Biota, Archaea, Proteoarchaeota, Asgardarchaeota, Eukaryota, Neokaryota, Scotokaryota Opimoda, Podiata, Amorphea, Obazoa, Opisthokonta, Holozoa, Filozoa, Choanozoa, Animalia, Eumetazoa, Parahoxozoa, Bilateria, Nephrozoa, Protostomia, Ecdysozoa, Panarthropoda, Tactopoda, Arthropoda, Pancrustacea, Thylacocephala, Concavicarida, Concavicarididae

Referred Species: A. acutirostris, A. bandoi, A. chaohuensis, A. tatensis

Status: Extinct 

Time and Place: 250 to 247 Ma, in the Olenekian of the Early Triassic.

Ankitokazocaris is known from Madagascar, China, and Japan.

Physical Description: The first thing you might be thinking is “what the hell is that thing?” That, my friends, is a thylacocephalan. Thylacocephala was a clade of arthropods that lived from the Silurian to the Cretaceous. Most of their bodies were protected by a large carapace, which was open at the bottom. At the front of the carapace was an opening for the eyes. Three pairs of legs dangled down from the bottom of the carpace. These legs were not adapted for swimming, but for prey capture.

Ankitokazocaris is an average concavicaridan. The carapace had a rather large head opening at the front of the carapace, out of which two large eyes peeked. This opening was protected at the top by an extension of the carapace called the rostrum. Of the three raptorial limb pairs, the last pair was by far the largest. There were also several pairs of shorter legs at the back of the carapace. Unfortunately, a lot of anatomy such as what the gills and mouth looked like are unknown, because the carapace always covers these in the fossils

Diet: It is presumed that thylacocephalans like Ankitokazocaris were predatory. They had front limbs that would have been useful for grabbing small prey floating in the water.

Behavior: Very little is known about thylacocephalan behavior, in part because, well, look at them. As their limbs seem poorly-equipped for swimming vigorously, they probably hung out in the water column, going after any animals and detritus floating by. The large compound eyes would be good for seeing things floating in dim light. It’s possible that they rested on the seafloor during some periods of the day, rising up to catch prey.

Ecosystem: Ankitokazocaris probably lived in relatively shallow pelagic environments. Unfortunately not many other fossils have been found in Ankitokazocaris-bearing deposits, but these include ammonites, bivalves, and in Japan, other thylacocephalans such as Kitakamicaris and Ostenocaris.

Other: There’s still much that is unknown about thylacocephalans, such as many details of their softer anatomy and lifestyle and what their closest relatives are. The current consensus is that they’re probably crustaceans, but to my knowledge this has yet to be confirmed with phylogenetic analysis.

~ By Henry Thomas

Sources under the cut