46-416: Tamisiocarididae is a family of radiodonts , extinct marine animals related to arthropods , that bore finely-spined appendages that were presumably used in filter-feeding. When first discovered, the clade was named Cetiocaridae after a speculative evolution artwork, Bearded Ceticaris by John Meszaros, that depicted a hypothetical filter-feeding radiodont at a time before any were known to exist. However,
92-804: A horseshoe crab . Bands of setal blades with wrinkling lanceolate blades may have increased the surface area, suggesting they were gills , providing the animal's respiratory function. Abundance of the remains of scleritzed structures such as disarticulated frontal appendages and head sclerite complexes, suggest that mass moulting events may have occurred among radiodonts, a behavior which also has been reported in some other Cambrian arthropods such as trilobites . Radiodonts had diverse feeding strategies, which could be categorized as raptorial predators , sediment sifters, or suspension, filter feeders . For example, raptorial predators like Anomalocaris and Amplectobeluids might have been able to catch agile prey by using their raptorial frontal appendages;
138-618: A hurdiid radiodont in recent analyses, as a species more closely related to euarthropods than other radiodonts (based on some putative euarthropod-like features found on Schinderhannes ). However, neither each of them were supported by later investigations. The radial mouthparts are not cycloneuralian-exclusive and more likely present result of convergent evolution or ecdysozoa n plesimorphy , since they also have been found in panarthropods such as tardigrade and some lobopodia ns; radiodonts lacking definitive euarthropod features such as trunk tergites and multiple head appendages, and
184-626: A suspension feeding lifestyle for the group. These radiodonts are some of the few known from sediments beyond the Cambrian period. This subfamily shows that following the Great Ordovician Biodiversification Event , which saw a rise in the plankton population in the worlds oceans, suspension feeding became more common in radiodonts then other feeding styles. It also seems that due to the evolution of new predators, like large nautiloid cephalopods, and other arthropod groups like
230-615: A clade including upper stem (e.g. fuxianhuiids and bivalved arthropods) and crown Euarthropoda (e.g. Artiopoda , Chelicerata and Mandibulata ). This interpretation is supported by numerous arthropod groundplan found on radiodonts and opabiniids, such as stalked compound eyes , digestive glands, trunk appendages forming by dorsal and ventral elements (precursor of arthropod biramous appendages). Compared to opabiniids, which possess posterior mouth opening and fused frontalmost appendages (comparable to euarthropod posterior-facing labrum /hypostome complex), radiodonts on
276-435: A group of lobopodians that bore robust frontal appendages and digestive glands, but no body flaps. Such intermediate forms between lobopodian and radiodont/euarthropod suggest that the total-group Arthropoda arose from a paraphyletic lobopodian grade, alongside the other two extant panarthropod phyla Tardigrada and Onychophora . Previous studies may suggest radiodonts as a group other than stem-arthropods, such as
322-407: A hitherto unknown phylum ; cycloneuralia n worms undergone convergent with arthropods (based on the cycloneuralian-like radial mouthparts); stem chelicerate euarthropods alongside megacheira ns also known as great appendage arthropods (based on the similarity between radiodont frontal appendages, megacheiran great appendages and chelicerae ); or Schinderhannes bartelsi , which resolved as
368-479: A length of 8.3 cm (3.3 in) An isolated frontal appendage of a hurdiid with a length less than half that of the juvenile Lyrarapax is known, but it is not known whether this specimen pertains to an adult. The largest known Cambrian radiodont was Amplectobelua , reaching lengths of up to 90 cm (35 in) based on an incomplete specimen. Anomalocaris canadensis was also relatively large, estimated up to 34.2–37.8 cm (13.5–14.9 in) long, and
414-518: A preference for warmer waters. Like most radiodonts, cetiocarids have spiny frontal appendages. However, in this family the auxiliary spines are fine and densely-arranged, which are modified for use in filter feeding like modern basking sharks and mysticete whales . For example, Tamisiocaris is estimated to have fed on prey roughly a millimeter in size. Caryosyntrips Anomalocarididae Amplectobeluidae Echidnacaris briggsi Tamisiocaris borealis Hurdiidae Tamisiocarididae
460-606: A prominent three-part tail. Some forms have gnathobasic trunk limbs. In 2014, the clade Radiodonta was defined phylogenetically as a clade including any taxa closer to Anomalocaris canadensis than Paralithodes camtschaticus . In 2019, it was redefined morphologically as animal bearing head carapace complex with central (H-) and lateral (P-) elements; outgrowths (endites) from frontal appendages bearing auxiliary spines; and reduced anterior flaps or bands of lamellae (setal blades) and strong tapering of body from anterior to posterior. Most radiodonts were significantly larger than
506-463: A row, forming bands of gill -like structures known as setal blades, covered the dorsal surface of each body segment. At least in Aegirocassis , each of the lanceolate blades are covered in wrinkles. The ventral flaps may be homologous to the endopod of the biramous limbs of euarthropods and lobopodous limbs (lobopods) of gilled lobopodians , and the dorsal flaps and setal blades may be homologous to
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#1732884629703552-409: A scissor-like slicing or grasping motion. Oral cones of radiodonts may have been used for suction and/or biting. Together with the great variety of frontal appendages in different species of radiodonts, differentiation of oral cones between species suggests preferences of different diets as well. For example, the triradial oral cone of Anomalocaris with irregular, tuberculated toothplates and
598-944: A small opening may have been adapted to small and nektonic prey, while the rigid tetraradial oral cones of Peytoia , Titanokorys , Hurdia , and one isolated oral cone attributed to Cambroraster with a larger opening and sometimes additional tooth plates may have been capable to consume larger food items relative to their body size and probably benthic or endobenthic prey. Priapulida [REDACTED] and relatives Onychophora [REDACTED] Tardigrada [REDACTED] Lobopodian grade ( paraphyletic ) [REDACTED] Siberiid lobopodians [REDACTED] Pambdelurion [REDACTED] Kerygmachela [REDACTED] Opabiniidae [REDACTED] Radiodonta [REDACTED] Euarthropoda [REDACTED] Most phylogenetic analyses suggest that radiodonts, alongside opabiniids ( Opabinia and Utaurora ), are stem-group arthropods just basal to deuteropoda ,
644-412: A tail fan in some species, may have helped steering and/or stabilizing the animal during locomotion. In Anomalocaris , morphology of the tail fan even suggests it could rapidly change its swimming direction efficiently. On the other hand, some hurdiids have features significantly specialized for a nektobenthic lifestyle, such as Cambroraster with its dome-like H-element similar to the carapace of
690-1013: A typical radial arrangement. Three head sclerite ( carapace ) complex formed by a central H-element (anterior sclerite or head shield) and a pair of P-elements (lateral sclerites) cover the dorsal and laterovental surface of the animal's head. The P-elements may connect to each other as well as the H-element by a narrow anterior extension (P-element neck or 'beak'). The head sclerites are small and ovoid in Anomalocarididae and Amplectobeluidae , but often enlarged in Hurdiidae , corresponded to their distinct body shapes (streamlined in Anomalocarididae/Amplectobeluidae but often compact in Hurdiidae). The head bore two stalked compound eyes , which may have had mobility, and are located between
736-421: A wheel" and Greek for odoús "tooth") refers to the radial arrangement of tooth plates (oral cone) surrounding the mouth, although these features are suggested to be absent in some radiodont species. The original diagnosis of order Radiodonta in 1996 is as follows: Radiodontids are bilaterally symmetrical, elongate arthropods with a nonmineralized cuticle typically most robust in the jaws and claws. The body
782-565: Is a subfamily of radiodonts (marine stem- arthropods ) from the lower Paleozoic era. It belongs to the larger hurdiidae (peytoiid) family, which were the most diverse and long lasting radiodonts. The members of this subfamily are restricted to the Lower Ordovician -aged Fezouata Formation of Morocco . Currently only two genera are included: Aegirocassis and Pseudoangustidontus . These two genera possess large Baleen -like auxiliary spines on their frontal appendages, which suggests
828-419: Is an extinct order of stem-group arthropods that was successful worldwide during the Cambrian period. Radiodonts are distinguished by their distinctive frontal appendages, which are morphologically diverse and were used for a variety of functions. Radiodonts were among the earliest large predators, but they also included sediment sifters and filter feeders. Some of the most famous species of radiodonts are
874-465: Is composed of multiple body segments, each associated with pairs of flaps and gill-like structures (setal blades). The anterior structures on the head are a pair of frontal appendages which have been referred to as 'claws', 'grasping appendages', 'feeding appendages', or 'great appendages' in previous studies (the last term is discouraged since the homology between frontal appendages and the original, morphologically distinct megacheiran great appendages
920-517: Is invalid. The family Tamisiocarididae was subsequently devised as a replacement name for the clade. Cetiocaridae was originally defined phylogenetically as all species more closely related to Tamisiocaris borealis than to Anomalocaris canadensis , Amplectobelua symbrachiata , or Hurdia victoria . Tamisocaridid fossils have been found in the Emu Bay Shale of Australia , Sirius Passet lagerstätte of Greenland , and Kinzers Formation of
966-692: Is known to have pediform trunk appendages (legs). The trunk has numerous body segments ( somites ), tapering from anterior to posterior, with the anterior three or four segments significantly constricted into a neck region. The trunk appendages were fin-like body flaps ('lateral flaps' or 'lobes' in some studies), usually one pair of ventral flaps per body segment, each slightly overlapping the one more anterior to it, but additional, non-overlapping sets of small dorsal flaps may occur in some Hurdiid species. The flaps may have numerous vein-like structures (referred to as 'strengthening rays', 'flap rays', 'tranverse rods', 'transverse lines' or 'veins' ). The flaps on
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#17328846297031012-531: Is questionable. ). They are sclerotized (hardened) and arthropodized (segmented), bearing ventral endites (spines) on most of their podomeres (segmental units), and the endites may bear additional rows of auxiliary spines on their anterior and posterior margins. The frontal appendage consists of two regions: the shaft ('peduncle', 'base' or 'promixal region' in some studies) and the distal articulated region (also referred to as 'claw' ). A triangular region covered by soft cuticle (arthrodial membrane) may occur on
1058-507: Is subdivided into two tagmata , much like the prosoma and opisthosoma of chelicerate arthropods. Typically, the front part shows no external segmentation, bears one pair of preoral claws, a pair of prominent eyes, and ventral jaws with radiating teeth. Some forms have additional rows of teeth and three or four postoral gnathobasic limb pairs. The trunk is metameric , typically with about 13 segments laterally developing imbricating lobes for swimming and gills for respiration, and may end in
1104-527: The Cambrian taxa Anomalocaris canadensis , Hurdia victoria , Peytoia nathorsti , Titanokorys gainesi , Cambroraster falcatus and Amplectobelua symbrachiata . The later surviving members include the subfamily Aegirocassisinae from the Early Ordovician of Morocco and the Early Devonian member Schinderhannes bartelsi from Germany. The name Radiodonta (Latin for radius "spoke of
1150-419: The eurypterids , the radiodonts evolved suspension feeding lifestyles in order to minimize competition for food. Aegirocassisines are distinguished by their frontal appendages possessing endites that bore long auxiliary spines (the longest of any radiodont). The appendages are composed of around six podomeres that each bore one endite. Although all of the members of this subfamily were suspension feeders,
1196-453: The Cambrian hurdiid Titanokorys approached around 50 cm (20 in) long. The body of a radiodont could be divided into two regions: head and trunk. The head is composed of only one body segment known as the ocular somite, covered by sclerites (head carapace complex), bore arthropodized frontal appendages, ventral mouthparts (oral cone), and stalked compound eyes . The tapering trunk
1242-469: The United States. Their fossils date to stage 3 and stage 4 of the Cambrian . Radiodonta Anomalocarida Radiodonta (also known as radiodonts , radiodontans , radiodontids , anomalocarids , or anomalocaridids , although the last two originally refer to the family Anomalocarididae , which previously included all species of this order but is now restricted to only a few species. )
1288-474: The arthropod stem lineage. The constricted neck region with feeding appendicular structures of some radiodont may also shed light on the origin of the sophisticated arthropod head, which was formed by the fusion of multiple anterior body segments. Basal deuteropods that possess a mixture of radiodont/opabiniid characters like Kylinxia and Erratus , may represent intermediate forms between radiodonts, opabiniids and other euarthropods. Taxa just basal to
1334-458: The brain composed of only one brain segment originating from the ocular somite, the protocerebrum. The nerves of the frontal appendages and compound eyes arose from the anterior and lateral regions of the brain. Based on Moysiuk & Caron 2022, the frontal appendage nerves arose from the ventral deutocerebrum, the second brain segment. The previous "frontal appendage nerves" actually represent median eye nerve. In both interpretations, posterior to
1380-459: The brain was a pair of apparently unfused ventral nerve cords which ran through the animal's neck region. Radiodonts were interpreted as nektonic or nektobenthic animals, with their morphology suggesting an active swimming lifestyle. The muscular, overlapping ventral flaps may have propelled the animal through the water, possibly by moving in a wave-like formation resembling modern rays and cuttlefish . Pairs of dorsal flaps, which make up
1426-415: The exite and gill-bearing dorsal flaps of the former taxa. The trunk may end either with a tail fan compose of 1 to 3 pairs of blades, a pair of long furcae, an elongated terminal structure, or a featureless blunt tip. Traces of muscles , digestive system and nervous system were described from some radiodont fossils. Pairs of well-developed muscles were connected to the ventral flaps located at
Tamisiocarididae - Misplaced Pages Continue
1472-535: The family name was not valid according to the International Code of Zoological Nomenclature , as no real genus named "Cetiocaris" exists, and in 2019 it was formally replaced by the name Tamisiocarididae, after the only valid genus of the clade at the time. The family is only known from Series 2 of the Cambrian , unlike other radiodont families, which persisted longer into the Cambrian. All known species would have lived in tropical or subtropical waters, suggesting
1518-417: The gaps formed by the posterior regions of the H-element and P-elements. The compound eyes of Echidnacaris are exceptionally unstalked. Some species possess an additional median eye behind the H-element. Contrary to the original diagnosis, the division of body segments (segmental boundaries) can be visible externally and no known member of Radiodonta (except the putative radiodont Cucumericrus )
1564-470: The lateral cavities of each body segment. Between the lateral muscles is a sophisticated digestive system, formed by a widening of the foregut and hindgut, both connected by a narrow midgut associated with six pairs of gut divercula (digestive glands). The brain of radiodonts was simpler than the three-segmented (compose of pro-, deuto- and tritocerebrum) brains of euarthropods , but further interpretations differ between studies. Based on Cong et al. 2014,
1610-432: The latter even bore a robust endite for holding prey like a pincer . With the smaller head carapace complex and large surface of arthrodial membranes, frontal appendages of these taxa had greater flexibility. Stout frontal appendages of sediment sifters like Hurdia and Peytoia have serrated endites with mesial curvature, which could form a basket-like trap for raking through sediment and passing food items towards
1656-1041: The megacheiran great appendages were considered to be deutocerebral, which could be non-homologous to the radiodont protocerebral frontal appendages; putative euarthropod characters found on the single Schinderhannes fossil is questionable and may present other radiodont-like structures. Caryosyntrips [REDACTED] Houcaris saron [REDACTED] "Anomalocaris" briggsi [REDACTED] Tamisiocaris [REDACTED] Laminacaris [REDACTED] Houcaris magnabasis [REDACTED] Anomalocaris [REDACTED] Lyrarapax [REDACTED] Amplectobelua [REDACTED] "Anomalocaris" kunmingensis [REDACTED] Ramskoeldia consimilis [REDACTED] Ramskoeldia platyacantha [REDACTED] Paranomalocaris [REDACTED] Peytoia [REDACTED] cf. Peytoia [REDACTED] Stanleycaris [REDACTED] Schinderhannes [REDACTED] Aegirocassis [REDACTED] Aegirocassisinae Aegirocassisinae
1702-413: The morphology of the frontal appendages, especially those of the spines, always differs between species, it is one of the most important means of species identification. In fact, many radiodonts are only known from a handful of fossilized frontal appendages. The mouth is on the ventral side of the head, behind the attachment point of frontal appendages and is surrounded by a ring of tooth plates, forming
1748-508: The mouthpart known as oral cone ('jaws' in previous studies ). 3 or 4 tooth plates might be enlarged, giving the oral cone a triradial (e.g. Anomalocaris , Echidnacaris ) or tetraradial (e.g. Hurdiidae , Lyrarapax ) appearance. The inner margin of tooth plates have spikes facing towards the mouth opening. Additional rows of internal tooth plates may occur in some hurdiid genera. Detail reconstruction of some amplectobeluid oral cones are speculative, but they possibly did not present
1794-399: The neck region (referred to as 'reduced flaps', 'neck flaps', 'head flaps', 'anterior flaps' or 'differentiated flaps' ) are significantly reduced. In some species, jaw-like feeding appendages called gnathobase-like structures (GLSs) arose from each of the bases of their reduced neck flaps. Numerous elongated blade-like extensions (referred to as lanceolate blades or lamellae ) arranged in
1840-454: The other Cambrian fauna, with typical body lengths of large taxa varying from 30 to 50 cm (12 to 20 in). The largest described radiodont is the Early Ordovician species Aegirocassis benmoulai , which may have grown up to 2 m (6.6 ft) long. A nearly complete specimen of a juvenile Lyrarapax unguispinus measured only 18 mm (0.71 in), making it among the smallest radiodont specimens known, though adults reached
1886-404: The other hand featured euarthropod-like dorsal sclerite (H-element) and arthropodization (frontal appendages) on their head regions, alongside cuticularized gut termini. The fact that both radiodonts and opabiniids lack exoskeleton on their trunk region suggests that the origin of compound eyes and arthropodization (segmented appendages) precede arthrodization (full set of trunk exoskeleton) in
Tamisiocarididae - Misplaced Pages Continue
1932-613: The radiodont, opabiniid and euarthropod branch are ' gilled lobopodians ' like Pambdelurion and Kerygmachela , which occasionally united under the class Dinocaridida with opabibiids and radiodonts. They have body flaps, digestive glands, large (presumely compound) eyes and specialized frontal appendages like the former taxa, but their frontal appendages are not arthropodized nor fused, eyes sessile, gill-like structures less prominent, and certainly bore lobopod underneath each of their flaps. Taxa even basal to 'gilled lobopodians' are siberiids like Megadictyon and Jianshanopodia ,
1978-429: The study notes that other suspension feeding radiodonts (like Tamisiocaris ) are not included in this subfamily. This subfamily is named after Aegirocassis and not Pseudoangustidontus , as even though the latter was named before the former, Pseudoangustidontus was previously considered enigmatic before the 2023 studies publication. The aegirocassisines were some of the largest radiodonts, with Aegirocassis reaching
2024-477: The ventral side between podomeres and provide flexibility. Their purported pre-ocular and protocerebral origin suggest they are homologous to the primary antennae of Onychophora and the labrum of Euarthropoda (all arose from ocular somite ), while subsequent studies also suggest a deutocerebral origin and homologous with the chelicerae of Chelicerata and the antennae or ' great appendages ' of other arthropods (all arose from post-ocular somite 1). Since
2070-489: The well-developed oral cone. Endites of frontal appendages from suspension/filter feeders like Tamisiocaris and Aegirocassis have flexible, densely-packed auxiliary spines, which could filter out organic components such as mesozooplankton and phytoplankton down to 0.5mm. Frontal appendages of Caryosyntrips , which are unusual for radiodonts in having the direction of endite-bearing surfaces opposing one another and may have been able to manipulate and crush prey in
2116-413: Was originally named Cetiocaridae. In the 2013 speculative paleoart book All Your Yesterdays , paleoartist John Meszaros depicted a hypothetical filter-feeding anomalocaridid he named "Ceticaris". This artwork inspired the name of Cetiocaridae. However, as no genus "Cetiocaris" actually exists, the name Cetiocaridae does not comply with article 29 of the International Code of Zoological Nomenclature and
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