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Description

As many know well the Cambrian is the beginning of our world’s biodiversity, an huge evolutionary leap from the last 30 million years of the Ediacaran under the ocean, the major period of life diversification with the “explosion” and rise of the many major clades of animals that would establish for the next 500 million years, such as mollusks, annelids, arthropods, chordates, etc. as well alongside them some other very bizarre clades that arose and at the same time perished in that span which couldn’t leave any descendant after.
Marine life grew up from its simple and fractal beginnings and became more from the pacific soft bodies sessile, slow filter feeders and detritivorous ediacarans stuck in the sand, radiating into a crazy mosaic of different shelled creatures nothing like anything that appeared before and establishing the bases for the dominant clades today, with different shapes, number of legs, shape of eyes, segments, jawed, it was mostly the age of arthropods and relatives as they composed most of the diversity of major fauna in many key niches like trilobites, the first arachnids and crustaceans and many others unique forms of this period. Although this didn’t hide the diversity of other organisms in other realms, as even if many species still developed huge anatomical innovations of shape and forms, the first mollusks extending thought he mud, the first large reefs formed by variety of sponges and sponge like organisms, the first strange echinoderms that were totally apart of any living species, and chordates which even though they started insignificant their derived notochord would bring secure their success.

For this chart I wanted to do something more than just pick the few largest animals of period which excess the meter long (which could have been just 2 specie), so I tried to see specimen size from all other clades known from the period, giving more variety of what some of the biggest animals were, even if they weren’t gigantic like most of actual fauna, of course with this I have to be a bit selective as not many clades really became enough large.

The world in this point was pretty much the world of the Panarthropods, the major clade that includes all known Arthropoda, Tardigrada and Onychophora that had its genesis in the cambrian, as well different paraphyletic groups that lived across the Paleozoic, many of these characterized mostly for possess multiple amounts of limbs, some with claws, ventral nervous system, segmented body with distinguishable head and trunk. The most characteristic group of Panarthropods of this period were the Lobopodians, an informal taxon of high prolific species that dominated though the Cambrian in different ecological levels this thanks to their extravagant morphological adaptations including a variety of mouthparts and appendages for feeding as well as the development of varied limbs for mobility or swimming.
Radiodonts were mostly nektonic carnivores characterized by having elongated grasping appendages possessing ventral spines labeled as “endites” that allowed them to catch their prey and/or feed, an oral cone formed by different mouth pieces, complex eyes that protrude from the head by means of short eye stalks, multiple fin-like body flaps that varied and shape in arrangement depending on the species. They are the major megafauna’ organisms of the time, with species reaching the decimeters. People is probably familiar with the most iconic genus Anomalocaris, being known as one of the first apex predators of history, the species A. canadensis as this large species of around 1 m considered to be one of the largest species followed by A. saron from China which has been calculated to be 2 m long, but the reality is far from these measurements as many specimens and scales done over the years had become inaccurate due to specimens being not properly scaled in proportion, as well many specimens of large size has been reclassified due to belong to totally different species, even different families as with new data and analysis it was found this group was more diverse and had a totally different relationship from what was once considered.
At this point there are 4 distinguishable clades named (although affinity could change in subsequent studies from the date of this publication)
-Anomalocaridids were the first group erected which once included all species until new phylogenic analysis changed it, now it only host some species of the genus Anomalocaris, one of the most famous as mentioned before being A. canadensis from Laurentia most of the average specimens reach sizes of around 40 cm with appendages of 14 cm, there are some even larger individuals such as the dubious A. gigantea with had appendages of around 20 cm in length, scaling with smaller individuals it gives a total body size of 70 cm.
- Amplectobeluids represented a peculiar type of predatory radiodonts which some species had high derived appendages able to grasp thanks to their specialized elongated hooked endite that with the rest of the appendage adopt a pincer-like shape, gnathobase-like structures behind their oral cones, as well their flaps that are elongated in the front and decrease gradually giving it a kite shape, which could have made them quite impressive and agile predators predators, in this category includes, some of the largest anomalocarids like Amplectobelua symbrachiata with species had shorter frontal appendages and very elongated hooked endites most described specimens are small but there are undescribed specimens with appendages size of 10 to 15 cm giving it a total size of 60 cm, and Ramskoeldia platyacantha which seems to have had a more basic appendage form which didn’t possess a hooked endite, but still would have reached some considerable sizes due the largest appendages are around 20 cm in length, they could have grown around 70 cm in length.
- Hurdiids are the most diverse of all the groups able to live beyond the Cambrian, counting with different genus and species, they are characterized by their elongated head carapace which depending of the ecological niches and lifestyle adopted peculiar shapes and their specialized uniform brush like frontal appendages which instead of being prominent in the front they had a reduced size and were found below the carapace, short flaps that in some species had a double pair in the edges of the body and lack of fluke tail. There are some well know species like the spearhead-shaped Hurdia, and recent new ones like the horseshoe-shaped dorsal carapace Cambroraster, this last is related to other even bigger species known for its enormous Carapace preserved which is still undescribed, is dubbed as “The Mothership” and in life it could have reached around 55 cm in length.
- Tamisiocaridids are a very cryptic group of radiodonts which are mostly known for their appendages with all of the body still unknown (being probably considered to be Hurdiid-like for their proximity to this group) these are characterized for their elongated and combed spines on their feeding appendages which allowed them to filter feed. Although the group is named after Tamisiocaris borealis, the largest species of this group belongs to the other species hinted within this, “Anomalocaris” briggsi which has been considered to be within this clade this had appendages of about 15 cm, with a probable size of about 45 cm.
One of the biggest radiodonts known is a fragmentary one, with still conflicting affinity being considered to be basal to Amplectobeluids: Laminacaris chimera, once named as A. saron it has one of the largest appendages known of this group with a size of around 30 cm, scaled with anomalocarids proportions it gives an approximated size of around 80 to 90 cm in length.

A tentative competitor that could dethrone radiodonts as the biggest predators as well the biggest animal of the period are some species of Non-radiodont Dinocaridids, an aggrupation that includes many benthos species like Opabinia regalis (which was around 7 cm in length), this monster is Omnidens amplus (originally classified as a worm) is only know by a preserved set of mouthparts scaled up with some relatives with better complete specimens like the benthonic dweller Pambdelurion whittingtoni of around 56 cm gives a possible body size estimation of 1.5 to 2 meters long, of course being this high speculative for the lack of a complete or at least good specimen.

Alongside the Panarthropods were also the myriad species of Arthropods, most of them were in the genesis of the clades that could come up millions of years after, just like Crustaceans, Chelicerata or Mandibulata, but in this point on time these weren’t yet a thing like they would be in next periods. The diversity of these was formed by other clades, specially a lot of stem-group outside euarthropods and still unknown to link clades as well others euarthropods unrelated to the major clades mentioned first; the pelagic bivalve arthropod Tuzoiid Tuzoia sp. was able to reach 18 cm long, the benthonic Sidneyia inexpectans with specimens reaching up 16 cm long, the genus Branchiocaris pretiosa which reached up sizes around 15 cm long, and the Aglaspidid Beckwithia typa with specimens reaching around sizes of 12 to 20 cm in length. Although most of these early arthropods weren’t giants, they still were pretty large among their groups.
Trilobites are one if not the major clade of arthropods for excellence during the Paleozoic, with different variety of species, being the Cambrian the pinnacle of its population clades with more than 60 families, most of these were around the lengths of less than 10 cm but in some points they were able to reach a very extraordinary size from Lochmanolenellus mexicana with a length 24 cm was one of the largest animals known of the lower Cambrian, to one of the biggest species Acadoparadoxides briaerus from morocco, with specimens reaching up 45 cm long. Apart of trilobites, there were some other relatives which belongs to a major clade known as “Trilobitomorpha” which resemble them in certain anatomical features, but they weren’t true trilobites, such as the bottom dwelling Helmetiid Helmetia expansa, a very large soft-bodied looking arthropod of around 27 cm long is one of the largest non-anomalocarids arthropods of burgers shell, and the nektonic Tegopeltidae Tegopelte gigas with a size of 19 cm.

The Archaeopriapulida (stem-priapulids) were other of the predatory benthonic animals of the Cambrian landscape, pretty much found burrowing in the sand and mud and protruding from their places, exposing a large proboscis they were mostly ambush hunters. The most well-known is probably Ottoia for the common of its specimens, but these often doesn’t pass the length of 8 to 15 cm, but others were bigger that this one, a good example is the species Louisella pedunculata, which the largest specimen reached a size of 30 cm long with the proboscis extended.

One odd group among the Cambrian biota was the Vetulicolians, an enigmatic clade probably related to deuterostomes. These were weird arthropod-looking creatures that show adaptations for nektonic lifestyle and mostly being suspension feeders, many of these tended to be average lengths less than 10 cm, but Yuyuanozoon magnificissimi from comes to be the largest species known, with a length of 20.2 cm
The Chordates diversity during the Cambrian was formed by a small group of vermin agnatha forms, mostly swimming filter feeding of small size of few centimeters, the largest of these was Metaspriggina with specimens reaching up to 10 cm long which wasn’t that large size compared to many Cambrian lifeforms and even more to their successors, but was still an outstanding length compared to other of the chordates of the period.

Echinoderms were in their early genesis of its diversification with some unique morphology, so bizarre and extravagant compared to most of the current species, as well there were others similar or very close in many aspect to actual ones; although most were very minuscule, some of the few macroscopic forms included species like Lyracystis radiata which is the largest eocrinoid with specimens reaching up sizes to 21 cm tall being half of its size their fibrous comb-like arms extended in a Y shaped branched arm.

Lophotrochozoa flourished during this period, evolving into the important clades including the very common brachiopods, the basic annelids and the Mollusks, although there were some species that could be classified as the last ancestors or stem-relatives of such clades, they don’t belong to these clades but they are coming to the roots of these, including Odontogriphus which specimens were able to reach up sizes around 12 cm long. Mollusks started their slow path into diversification with early small shelled varieties, most of them minuscule and don’t reaching up few centimeters of length, although few reached some considerable size for the average, such as the pelagic Nectocaris pteryx, the enigmatic cephalopod-like mollusk (?) with specimens reaching up sizes of 7 cm long, then there were the earliest cephalopods, at this point they were just less similar to any living species and more like a sort of snail-like mollusks crawling through the bottom, probably with some primitive tentacles protruding of their mantle, these early species belong to the clade Plectronocerida, a group characterized by their straight or semi curves shells of very minuscule size, with specimens preserving the inner structure that correlates with other early shelled cephalopods, although from these there is some considerable large species, like Physalactinoceras compressum which had a shell size of 18 cm length.

Cnidarians are among the oldest animals on earth, probably appearing during the Ediacaran, although we will find their remains around the Cambrian, being quite successful though the warm oceans either as jellyfish or small coral-like forms; among some of the large species there was the still disputed in affinity Echmatocrinus which is a pretty robust sessile species with a height of 18 cm.

Archaeocyathids were a group formed mostly by small conical shaped forms with some brachiating forms, similar in many ways to sponges being benthonic sessile animals, they are characteristic of the period as they appeared on the beginning and became one of the characteristic reef building organisms though the early and middle cambrian until they declined and became totally extinct at the end. Many of these often reached sizes of around 9 to 10 cm tall and some centimeters in diameter, with giant flattened specie such as Okulitchicyathus discoformis which was able to reach diameters of around 50 cm, and probably reaching around 1.5 meters in diameter.

Sponges were one of the major reef builders of the Cambrian on the middle and late Cambrian after the down of Archaeocyathids, forming alongside other sessile lifeforms extensive biomes which thrived in the warm swallow oceans. Some of the biggest sponges found so far of this period belong to the species Quadrolaminiella diagonalis which were barrel shaped sponge from the Chengjiang Fauna, with a height of 20 cm and a diameter of around 12 cm. Another genus was Leptomitus, a very cosmopolitan demosponge very characteristic of burgess shale with variety of species, although the largest species would belong to tall and thin looking forms from the species L. lineatus with specimens reaching up heights around 36.4 cm, but with a diameter less than a centimeter long.

References
- Briggs, D. E. (1972). Anomalocaris, the largest known Cambrian arthropod. Palaeontology, 22(3), 631-664.
-Vinther, J., Porras, L., Young, F. J., Budd, G. E., & Edgecombe, G. D. (2016). The mouth apparatus of the Cambrian gilled lobopodian Pambdelurion whittingtoni. Palaeontology, 59(6), 841-849.
-Guo, J., Pates, S., Cong, P., Daley, A. C., Edgecombe, G. D., Chen, T., & Hou, X. (2019). A new radiodont (stem Euarthropoda) frontal appendage with a mosaic of characters from the Cambrian (Series 2 Stage 3) Chengjiang biota. Papers in Palaeontology, 5(1), 99-110.
-Cong, P. Y., Edgecombe, G. D., Daley, A. C., Guo, J., Pates, S., & Hou, X. G. (2018). New radiodonts with gnathobase‐like structures from the Cambrian Chengjiang biota and implications for the systematics of Radiodonta. Papers in Palaeontology, 4(4), 605-621.
- Xianguang, H., Bergström, J., & Jie, Y. (2006). Distinguishing anomalocaridids from arthropods and priapulids. Geological Journal, 41(3‐4), 259-269.
-Whittington, H. B. (1985). Tegopelte gigas, a second soft-bodied trilobite from the Burgess Shale, Middle Cambrian, British Columbia. Journal of Paleontology, 1251-1274.
-Bruton, D. L. (1981). The arthropod Sidneyia inexpectans, Middle Cambrian, Burgess Shale, British Columbia. Philosophical Transactions of the Royal Society of London. B, Biological Sciences, 295(1079), 619-653.
- Vannier, J., Caron, J. B., Yuan, J. L., Briggs, D. E., Collins, D., Zhao, Y. L., & Zhu, M. Y. (2007). Tuzoia: morphology and lifestyle of a large bivalved arthropod of the Cambrian seas. Journal of Paleontology, 81(3), 445-471.
- Rudkin, D. M., Young, G. A., Elias, R. J., & Dobrzanski, E. P. (2003). The world's biggest trilobite—Isotelus rex new species from the Upper Ordovician of northern Manitoba, Canada. Journal of Paleontology, 77(1), 99-112.
- Daley, A. C., Antcliffe, J. B., Drage, H. B., & Pates, S. (2018). Early fossil record of Euarthropoda and the Cambrian Explosion. Proceedings of the National Academy of Sciences, 115(21), 5323-5331.
- Aria, C., & Caron, J.-B. (2017). Burgess Shale fossils illustrate the origin of the mandibulate body plan. Nature, 545(7652), 89–92.
-Walcott, C. D. (1911). Cambrian Geology and Paleontology II: No. 5--Middle Cambrian Annelids.
-Morris, S. C., & Caron, J. B. (2014). A primitive fish from the Cambrian of North America. Nature, 512(7515), 419.
- Sprinkle, J., & Collins, D. (2006). New eocrinoids from the Burgess Shale, southern British Columbia, Canada, and the Spence Shale, northern Utah, USA. Canadian Journal of Earth Sciences, 43(3), 303-322.
- Sprinkle, J., & Collins, D. (1998). Revision of Echmatocrinus from the middle Cambrian burgess shale of British Columbia. Lethaia, 31(4), 269-282.
- Caron, J. B., Scheltema, A., Schander, C., & Rudkin, D. (2006). A soft-bodied mollusc with radula from the Middle Cambrian Burgess Shale. Nature, 442(7099), 159.
- Walcott, C. D. (1917). Middle Cambrian Spongiae. Smithsonian Miscellaneous Collections.
- Legg, D. A., Sutton, M. D., & Edgecombe, G. D. (2013). Arthropod fossil data increase congruence of morphological and molecular phylogenies. Nature communications, 4, 2485.
--Klug, C., De Baets, K., Kröger, B., Bell, M. A., Korn, D., & Payne, J. L. (2015). Normal giants? Temporal and latitudinal shifts of Palaeozoic marine invertebrate gigantism and global change. Lethaia, 48(2), 267-288.
- Wu, W., Zhu, M., & Steiner, M. (2014). Composition and tiering of the Cambrian sponge communities. Palaeogeography, Palaeoclimatology, Palaeoecology, 398, 86-96.

-Cordie, D. R., & Dornbos, S. Q. (2019). Restricted morphospace occupancy of early Cambrian reef-building archaeocyaths. Paleobiology, 45(2), 331-346.

Description

As many know well the Cambrian is the beginning of our world’s biodiversity, an huge evolutionary leap from the last 30 million years of the Ediacaran under the ocean, the major period of life diversification with the “explosion” and rise of the many major clades of animals that would establish for the next 500 million years, such as mollusks, annelids, arthropods, chordates, etc. as well alongside them some other very bizarre clades that arose and at the same time perished in that span which couldn’t leave any descendant after.
Marine life grew up from its simple and fractal beginnings and became more from the pacific soft bodies sessile, slow filter feeders and detritivorous ediacarans stuck in the sand, radiating into a crazy mosaic of different shelled creatures nothing like anything that appeared before and establishing the bases for the dominant clades today, with different shapes, number of legs, shape of eyes, segments, jawed, it was mostly the age of arthropods and relatives as they composed most of the diversity of major fauna in many key niches like trilobites, the first arachnids and crustaceans and many others unique forms of this period. Although this didn’t hide the diversity of other organisms in other realms, as even if many species still developed huge anatomical innovations of shape and forms, the first mollusks extending thought he mud, the first large reefs formed by variety of sponges and sponge like organisms, the first strange echinoderms that were totally apart of any living species, and chordates which even though they started insignificant their derived notochord would bring secure their success.

For this chart I wanted to do something more than just pick the few largest animals of period which excess the meter long (which could have been just 2 specie), so I tried to see specimen size from all other clades known from the period, giving more variety of what some of the biggest animals were, even if they weren’t gigantic like most of actual fauna, of course with this I have to be a bit selective as not many clades really became enough large.

The world in this point was pretty much the world of the Panarthropods, the major clade that includes all known Arthropoda, Tardigrada and Onychophora that had its genesis in the cambrian, as well different paraphyletic groups that lived across the Paleozoic, many of these characterized mostly for possess multiple amounts of limbs, some with claws, ventral nervous system, segmented body with distinguishable head and trunk. The most characteristic group of Panarthropods of this period were the Lobopodians, an informal taxon of high prolific species that dominated though the Cambrian in different ecological levels this thanks to their extravagant morphological adaptations including a variety of mouthparts and appendages for feeding as well as the development of varied limbs for mobility or swimming.
Radiodonts were mostly nektonic carnivores characterized by having elongated grasping appendages possessing ventral spines labeled as “endites” that allowed them to catch their prey and/or feed, an oral cone formed by different mouth pieces, complex eyes that protrude from the head by means of short eye stalks, multiple fin-like body flaps that varied and shape in arrangement depending on the species. They are the major megafauna’ organisms of the time, with species reaching the decimeters. People is probably familiar with the most iconic genus Anomalocaris, being known as one of the first apex predators of history, the species A. canadensis as this large species of around 1 m considered to be one of the largest species followed by A. saron from China which has been calculated to be 2 m long, but the reality is far from these measurements as many specimens and scales done over the years had become inaccurate due to specimens being not properly scaled in proportion, as well many specimens of large size has been reclassified due to belong to totally different species, even different families as with new data and analysis it was found this group was more diverse and had a totally different relationship from what was once considered.
At this point there are 4 distinguishable clades named (although affinity could change in subsequent studies from the date of this publication)
-Anomalocaridids were the first group erected which once included all species until new phylogenic analysis changed it, now it only host some species of the genus Anomalocaris, one of the most famous as mentioned before being A. canadensis from Laurentia most of the average specimens reach sizes of around 40 cm with appendages of 14 cm, there are some even larger individuals such as the dubious A. gigantea with had appendages of around 20 cm in length, scaling with smaller individuals it gives a total body size of 70 cm.
- Amplectobeluids represented a peculiar type of predatory radiodonts which some species had high derived appendages able to grasp thanks to their specialized elongated hooked endite that with the rest of the appendage adopt a pincer-like shape, gnathobase-like structures behind their oral cones, as well their flaps that are elongated in the front and decrease gradually giving it a kite shape, which could have made them quite impressive and agile predators predators, in this category includes, some of the largest anomalocarids like Amplectobelua symbrachiata with species had shorter frontal appendages and very elongated hooked endites most described specimens are small but there are undescribed specimens with appendages size of 10 to 15 cm giving it a total size of 60 cm, and Ramskoeldia platyacantha which seems to have had a more basic appendage form which didn’t possess a hooked endite, but still would have reached some considerable sizes due the largest appendages are around 20 cm in length, they could have grown around 70 cm in length.
- Hurdiids are the most diverse of all the groups able to live beyond the Cambrian, counting with different genus and species, they are characterized by their elongated head carapace which depending of the ecological niches and lifestyle adopted peculiar shapes and their specialized uniform brush like frontal appendages which instead of being prominent in the front they had a reduced size and were found below the carapace, short flaps that in some species had a double pair in the edges of the body and lack of fluke tail. There are some well know species like the spearhead-shaped Hurdia, and recent new ones like the horseshoe-shaped dorsal carapace Cambroraster, this last is related to other even bigger species known for its enormous Carapace preserved which is still undescribed, is dubbed as “The Mothership” and in life it could have reached around 55 cm in length.
- Tamisiocaridids are a very cryptic group of radiodonts which are mostly known for their appendages with all of the body still unknown (being probably considered to be Hurdiid-like for their proximity to this group) these are characterized for their elongated and combed spines on their feeding appendages which allowed them to filter feed. Although the group is named after Tamisiocaris borealis, the largest species of this group belongs to the other species hinted within this, “Anomalocaris” briggsi which has been considered to be within this clade this had appendages of about 15 cm, with a probable size of about 45 cm.
One of the biggest radiodonts known is a fragmentary one, with still conflicting affinity being considered to be basal to Amplectobeluids: Laminacaris chimera, once named as A. saron it has one of the largest appendages known of this group with a size of around 30 cm, scaled with anomalocarids proportions it gives an approximated size of around 80 to 90 cm in length.

A tentative competitor that could dethrone radiodonts as the biggest predators as well the biggest animal of the period are some species of Non-radiodont Dinocaridids, an aggrupation that includes many benthos species like Opabinia regalis (which was around 7 cm in length), this monster is Omnidens amplus (originally classified as a worm) is only know by a preserved set of mouthparts scaled up with some relatives with better complete specimens like the benthonic dweller Pambdelurion whittingtoni of around 56 cm gives a possible body size estimation of 1.5 to 2 meters long, of course being this high speculative for the lack of a complete or at least good specimen.

Alongside the Panarthropods were also the myriad species of Arthropods, most of them were in the genesis of the clades that could come up millions of years after, just like Crustaceans, Chelicerata or Mandibulata, but in this point on time these weren’t yet a thing like they would be in next periods. The diversity of these was formed by other clades, specially a lot of stem-group outside euarthropods and still unknown to link clades as well others euarthropods unrelated to the major clades mentioned first; the pelagic bivalve arthropod Tuzoiid Tuzoia sp. was able to reach 18 cm long, the benthonic Sidneyia inexpectans with specimens reaching up 16 cm long, the genus Branchiocaris pretiosa which reached up sizes around 15 cm long, and the Aglaspidid Beckwithia typa with specimens reaching around sizes of 12 to 20 cm in length. Although most of these early arthropods weren’t giants, they still were pretty large among their groups.
Trilobites are one if not the major clade of arthropods for excellence during the Paleozoic, with different variety of species, being the Cambrian the pinnacle of its population clades with more than 60 families, most of these were around the lengths of less than 10 cm but in some points they were able to reach a very extraordinary size from Lochmanolenellus mexicana with a length 24 cm was one of the largest animals known of the lower Cambrian, to one of the biggest species Acadoparadoxides briaerus from morocco, with specimens reaching up 45 cm long. Apart of trilobites, there were some other relatives which belongs to a major clade known as “Trilobitomorpha” which resemble them in certain anatomical features, but they weren’t true trilobites, such as the bottom dwelling Helmetiid Helmetia expansa, a very large soft-bodied looking arthropod of around 27 cm long is one of the largest non-anomalocarids arthropods of burgers shell, and the nektonic Tegopeltidae Tegopelte gigas with a size of 19 cm.

The Archaeopriapulida (stem-priapulids) were other of the predatory benthonic animals of the Cambrian landscape, pretty much found burrowing in the sand and mud and protruding from their places, exposing a large proboscis they were mostly ambush hunters. The most well-known is probably Ottoia for the common of its specimens, but these often doesn’t pass the length of 8 to 15 cm, but others were bigger that this one, a good example is the species Louisella pedunculata, which the largest specimen reached a size of 30 cm long with the proboscis extended.

One odd group among the Cambrian biota was the Vetulicolians, an enigmatic clade probably related to deuterostomes. These were weird arthropod-looking creatures that show adaptations for nektonic lifestyle and mostly being suspension feeders, many of these tended to be average lengths less than 10 cm, but Yuyuanozoon magnificissimi from comes to be the largest species known, with a length of 20.2 cm
The Chordates diversity during the Cambrian was formed by a small group of vermin agnatha forms, mostly swimming filter feeding of small size of few centimeters, the largest of these was Metaspriggina with specimens reaching up to 10 cm long which wasn’t that large size compared to many Cambrian lifeforms and even more to their successors, but was still an outstanding length compared to other of the chordates of the period.

Echinoderms were in their early genesis of its diversification with some unique morphology, so bizarre and extravagant compared to most of the current species, as well there were others similar or very close in many aspect to actual ones; although most were very minuscule, some of the few macroscopic forms included species like Lyracystis radiata which is the largest eocrinoid with specimens reaching up sizes to 21 cm tall being half of its size their fibrous comb-like arms extended in a Y shaped branched arm.

Lophotrochozoa flourished during this period, evolving into the important clades including the very common brachiopods, the basic annelids and the Mollusks, although there were some species that could be classified as the last ancestors or stem-relatives of such clades, they don’t belong to these clades but they are coming to the roots of these, including Odontogriphus which specimens were able to reach up sizes around 12 cm long. Mollusks started their slow path into diversification with early small shelled varieties, most of them minuscule and don’t reaching up few centimeters of length, although few reached some considerable size for the average, such as the pelagic Nectocaris pteryx, the enigmatic cephalopod-like mollusk (?) with specimens reaching up sizes of 7 cm long, then there were the earliest cephalopods, at this point they were just less similar to any living species and more like a sort of snail-like mollusks crawling through the bottom, probably with some primitive tentacles protruding of their mantle, these early species belong to the clade Plectronocerida, a group characterized by their straight or semi curves shells of very minuscule size, with specimens preserving the inner structure that correlates with other early shelled cephalopods, although from these there is some considerable large species, like Physalactinoceras compressum which had a shell size of 18 cm length.

Cnidarians are among the oldest animals on earth, probably appearing during the Ediacaran, although we will find their remains around the Cambrian, being quite successful though the warm oceans either as jellyfish or small coral-like forms; among some of the large species there was the still disputed in affinity Echmatocrinus which is a pretty robust sessile species with a height of 18 cm.

Archaeocyathids were a group formed mostly by small conical shaped forms with some brachiating forms, similar in many ways to sponges being benthonic sessile animals, they are characteristic of the period as they appeared on the beginning and became one of the characteristic reef building organisms though the early and middle cambrian until they declined and became totally extinct at the end. Many of these often reached sizes of around 9 to 10 cm tall and some centimeters in diameter, with giant flattened specie such as Okulitchicyathus discoformis which was able to reach diameters of around 50 cm, and probably reaching around 1.5 meters in diameter.

Sponges were one of the major reef builders of the Cambrian on the middle and late Cambrian after the down of Archaeocyathids, forming alongside other sessile lifeforms extensive biomes which thrived in the warm swallow oceans. Some of the biggest sponges found so far of this period belong to the species Quadrolaminiella diagonalis which were barrel shaped sponge from the Chengjiang Fauna, with a height of 20 cm and a diameter of around 12 cm. Another genus was Leptomitus, a very cosmopolitan demosponge very characteristic of burgess shale with variety of species, although the largest species would belong to tall and thin looking forms from the species L. lineatus with specimens reaching up heights around 36.4 cm, but with a diameter less than a centimeter long.

References
- Briggs, D. E. (1972). Anomalocaris, the largest known Cambrian arthropod. Palaeontology, 22(3), 631-664.
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