MOTH locality

Last updated
MOTH
Geologic site
'Wonder Block' cast (8 fossil fish individuals, of 7 species)..jpg
A cast of the "Wonder Block", a rock slab from MOTH with 7 different species (8 fish in total) in one place: [1]
an unnamed ischnacanthid (center left), an unnamed osteostracan (top left), Brochoadmones (two largest fish near the center), Lupopsyrus (above the left Brochoadmones), Drepanolepis (bottom center), Obtusacanthus (top right), Furcacauda (bottom right)
Canada relief map 2.svg
Red pog.svg
MOTH
Coordinates: 62°33′N127°45′W / 62.55°N 127.75°W / 62.55; -127.75
Location Northwest Territories, Canada
Age Lochkovian (Early Devonian)

The Man-on-the-hill (MOTH) locality is a fossil site in the Northwest Territories of Canada renowned for its incredibly well-preserved Early Devonian fish fossils. Discovered in the Mackenzie Mountains in the 1960s, MOTH accumulated greater prestige in the late 20th century, with many fossil fish species only known from this one site. The fauna consists of both jawed fish (mostly acanthodians, the "spiny sharks") and jawless fish (armored osteostracans and pteraspidomorphs, as well as distinctive fork-tailed furcacaudiform thelodonts). The geology of MOTH reconstructs the area as a calm marine environment with mixed sediment sources along the western coast of Laurussia. [2]

Contents

History

In the mid-1960s, geological mappers from the Geological Survey of Canada (GSC) discovered well-preserved fish fossils on a steep mountainside in the Mackenzie Mountains, about 70 km (43 mi) northeast from the mining town of Tungsten, Northwest Territories. At the time, the site was known as GSC locality 69014. [3] [4] [5] By the late 1970s, it had gained renown among Canadian paleoichthyologists, initiating a long list of new species discovered at the site. [5] [6]

The University of Alberta Laboratory for Vertebrate Paleontology (UALVP), which catalogues the site as UALVP locality 129, handled most subsequent collecting efforts. UA paleontologists Brian D.E. Chatterton and Mark V.H. Wilson led expeditions in 1983, 1990, 1996, 1998, and 2013, greatly increasing the volume of fossils recovered from the site. [7] A nearby rock landmark, resembling a man sitting on the ridge, inspired a persistent nickname for the site: Man-on-the-hill (MOTH). [8] [9] [10] The main fossiliferous section of MOTH is an Early Devonian horizon at the level of 180 meters, and fossils are also found on the talus slope of the mountainside. [2] Though MOTH is the most productive fish site in the Mackenzie Mountains, it is not alone: well-preserved Silurian fish are also known from lower layers of the site (known as B-MOTH), [11] [12] strata in the vicinity of Avalanche Lake, [13] [14] [9] [11] and elsewhere in the range. [5]

Geology

MOTH corresponds to a transitional zone between the clastic shales of the Road River Formation and the shelf carbonates of the Delorme Group. [2] An earliest Devonian (Lochkovian) age is established by its fossil fauna, with distinctive Lochkovian fish such as Waengsjoeaspis , Canadapteraspis , Romundina , Altholepis , Polymerolepis , and Seretolepis . Brachiopod and conodont fossils also agree with this age estimate. [8] At the time, the area would have been the tropical western continental shelf of Laurussia, fractured into many smaller basins and platforms by rifting along the Cordilleran front. [2]

The vertebrate-bearing layers of MOTH are mainly composed of finely layered light grey argillaceous (clay-rich) limestone and dark grey silty calcareous shale. Fine grains of dolomite, calcite, and quartz are the predominant minerals in the sediment, reflecting a mixture of carbonate and siliciclastic inputs, including sharp grains sourced from airborne dust. The layers are flat-lying and undisturbed apart from subtle bioturbation, indicating perpetually calm waters. Older studies advocated for a shallow-water (tide pool or lagoon) environment, based on the assumption that its fish and invertebrates preferred coastal or freshwater habitats. [5] A 2005 overview instead supported a more offshore environment, below storm wave base. In any case, the presence of pyrite indicates that bottom waters were anoxic (oxygen-deprived), allowing for high-fidelity fossil preservation. The exact cause of death is unknown for the fauna, as there is no evidence for turbidites (underwater mudslides) or seasonal water column disruptions. [2]

Paleobiota

More than 72 vertebrate species are known from MOTH as of 2015, though only around half have been formally named and described. [7]

Acanthodii

A few fully articulated ischnacanthiform fossils cannot be assigned to a specific species, as their diagnostic teeth are obscured by scales. Various MOTH ischnacanthid fossils have been referred to Ischnacanthus gracilis , though later studies refuted these claims. [15] [7] A 2001 UA biology dissertation by Gavin Hanke provides many new species names for MOTH specimens, but some of these names are yet to be published in a peer-reviewed journal. [16]

Acanthodians ("spiny sharks") and acanthodian-like fish of MOTH
GenusSpeciesNotesImages
Altholepis A. spp.Three new species from MOTH have scales resembling Altholepis, though these species have yet to be formally named and described. [17] [16] [18]
Brochoadmones [6] B. milesiA deep-bodied acanthodian with many small spiny "finlets" on its underside. [19] [1]
BrochoadmonesDB15 (cropped).jpg
Cassidiceps [19] C. vermiculatusA deep-bodied acanthodian with a head covered in thick densely-textured scales. [19]
Erymnacanthus [7] E. clivusAn ischnacanthid with small teeth and deep jaws. [7]
Erymnacanthus clivus jaw cast.jpg
Euryacanthus [7] E. rugosusAn ischnacanthid with large, robust teeth. [7] [20]
Gladiobranchus [6] G. probatonA toothless gladiobranchid diplacanthiform. Potentially a junior synonym of Uraniacanthus spinosus , an English acanthodian which is exceedingly similar to Gladiobranchus. [21] [22] [23]
Kathemacanthus [19] K. rosulentusA deep-bodied acanthodian with a "necklace" of artichoke-shaped scales similar to more typical chondrichthyans. [19] [24]
Lupopsyroides [25] L. macracanthusA toothless fish with simple scales and no apparent bony skeleton apart from fin spines. [16] [25]
Lupopsyrus [6] L. pygmaeusAn enigmatic acanthodian with simple scales and two rows of large keeled scutes on each side of its body. [26]
Nostolepis N. striataA weathered specimen with Nostolepis-type scales, yet to be formally described. [17] [16] The specimen may be referable to Nostovicina laticristata . [27]
Obtusacanthus [25] O. corroconisAn acanthodian-like fish with enlarged needle-like lip scales and no true teeth. [16] [25] [28]
Paucicanthus [29] P. vanelstiA narrow-bodied acanthodian lacking spines on its pectoral and pelvic fins. [29]
Polymerolepis P. whiteiAn enigmatic fish with "bradyodont"-like scales. Fossils from MOTH show that it had an anal fin spine, like acanthodians. [30]
Promesacanthus [10] P. eppleriA mesacanthid acanthodiform which retains small prepectoral spines, akin to "climatiiform" acanthodians. [10]
Seretolepis S. elegansA chondrichthyan-like fish closely related to Kathemacanthus. [24]
Tetanopsyrus [31] T. breviacanthias [21] A stocky diplacanthiform with broad crushing plates instead of teeth. This species has relatively short pectoral spines. [21]
T. lindoei [31] A stocky diplacanthiform with broad crushing plates instead of teeth. [31] This species has relatively long pectoral spines. [21]
Tetanopsyrus lindoei.png
Tricuspicanthus [7] T. gannitusA common but small ischnacanthid with three rows of teeth. [7] [20]
T. pisciculusA tiny ischnacanthid with two rows of teeth. [7]

Placoderms

Placoderms of MOTH
GenusSpeciesNotesImages
Romundina R. stellinaAn acanthothoracid placoderm. A single skull found at MOTH in 1990 has yet to be fully described. [8] [17] [32]
Romundina stellina.jpg

Osteostraci

Osteostracans of MOTH
GenusSpeciesNotesImages
Dentapelta [33] D. loeffleraeA superciliaspidid zenaspid with tooth-like denticles on its headshield. [33]
"Diademaspis""D." mackenziensis [8] A small zenaspid which is probably not a species of Diademaspis . [34] [35]
Glabrapelta [33] G. cristataA superciliaspidid zenaspid with a smooth headshield. [33]
G. minimaA small superciliaspidid zenaspid with a smooth headshield. [33]
Machairaspis M. serrata [36] A small scolenaspidine zenaspidid with a tall serrated spine in the middle of its headshield. [36]
Superciliaspis [8] S. gabrielsei [5] A superciliaspidid zenaspid with prominent spines on its headshield. Previously considered a species of Cephalaspis. [5] [8] [37] [33]
Waengsjoeaspis W. nahanniensis [8] An osteostracan related to Benneviaspidida. [8] [38]
W. platycornis [38] An osteostracan related to Benneviaspidida. [38]

Thelodonti

All of the thelodonts present at MOTH belong to the order Furcacaudiformes, a group characterized by small heads, humpbacked bodies which are deep and laterally flattened, and equally deep fork-shaped tails. [14] [9]

Thelodonts of MOTH
GenusSpeciesNotesImages
Cometicercus [9] C. talimaaaeA small, rare, and relatively slender furcacaudid furcacaudiform. [9]
Drepanolepis [9] D. maerssaeA tiny drepanolepidid [39] furcacaudiform with sickle-shaped scales. [9]
Drepanolepis maersae.jpg
Furcacauda [9] F. fredholmaeA medium-sized furcacaudid furcacaudiform with a pronounced dorsal fin. [9]
Furcacauda fredholmae.jpg
F. heintzae [5] A medium-sized furcacaudid furcacaudiform with a pronounced dorsal fin. Previously considered a species of Sigurdia . [5] [9]
Furcacauda heintzae.png
Sphenonectris [9] S. turneraeA relatively large furcacaudid furcacaudiform without a dorsal fin. [9]
Sphenonectris turnerae - MUSE.jpg

Pteraspidomorphi

Pteraspidomorphs of MOTH
GenusSpeciesNotesImages
Aserotaspis [5] A. canadensisA tesselate heterostracan with many small armor plates, each bearing a mesh of irregular ridges. [5]
Canadapteraspis [5] C. alocostomataA medium-sized pteraspidiform. [5]
Dinaspidella D. elizabethaeA common medium-sized irregulareaspidine cyathaspidid. [5] [40] [41]
Lepidaspis [5] L. serrataA tesselate heterostracan with many small armor plates, each bearing a single serrated ridge. [5]
Lepidaspis (jawless fish) cast.jpg
Nahanniaspis N. mackenziei [5] A common small irregulareaspidine cyathaspidid. [5] [40] [41]
Pionaspis P. amplissima [5] A rare relatively large cyathaspidid. [5]
Pionaspis amplissima (jawless fish) cast.jpg
Poraspis P. polarisA medium-sized poraspidine cyathaspidid. [5]

Other fossils

Conodonts are found at MOTH, including the Silurian-Pragian index fossil Ozarkodina remscheidensis . [17] [16] The most abundant invertebrates at MOTH are leperditiid ostracods which cluster together in mass death assemblages, sometimes around vertebrate remains. Various brachiopods can also be found at the site. Eurypterids are rare but well-preserved. [5] [2] Conulariids and phyllocarids have also been reported. [8] Tiny fragments of typical shallow marine invertebrates (crinoids, brachiopods, bryozoans, corals) make up a minor component of the sediment. [2]

References

  1. 1 2 Hanke, Gavin F.; Wilson, Mark V. H. (2006-09-11). "Anatomy of the early Devonian acanthodian Brochoadmones milesi based on nearly complete body fossils, with comments on the evolution and development of paired fins" . Journal of Vertebrate Paleontology. 26 (3): 526–537. doi:10.1671/0272-4634(2006)26[526:AOTEDA]2.0.CO;2. ISSN   0272-4634. S2CID   86378747.
  2. 1 2 3 4 5 6 7 Zorn, Marilyn E; Caldwell, Michael W; Wilson, Mark VH (2005-05-01). "Lithological analysis of the Lower Devonian vertebrate-bearing beds at the MOTH locality, N.W.T., Canada: insights to taphonomy and depositional setting". Canadian Journal of Earth Sciences. 42 (5): 763–775. doi:10.1139/e05-015. ISSN   0008-4077.
  3. ↑ Dineley, David L. (1967). "Palaeontology: Mackenzie Mountains, District of Mackenzie" (PDF). Geological Survey of Canada Report of Activities. 68 (1): 101.
  4. ↑ Gabrielse, H.; Blusson, S.L.; Roddick, J.A. (1973). "Geology of Flat River, Glacier Lake and Wrigley Lake map areas, District of Mackenzie, Northwest Territories" (PDF). Geological Survey of Canada Memoirs. 366: 1–268.
  5. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Dineley, D.L.; Loeffler, E.J. (1976). "Ostracoderm faunas of the Delorme and associated Siluro-Devonian formations North West territories Canada" (PDF). Special Papers in Palaeontology. 18: 1–214.
  6. 1 2 3 4 Bernacsek, G.M.; Dineley, D.L. (1977). "New acanthodians from the Delorme Formation (Lower Devonian) of N.W.T., Canada". Palaeontographica, Abteilung A. 159: 1–25.
  7. 1 2 3 4 5 6 7 8 9 10 Blais, Stephanie A.; Hermus, Chelsea R.; Wilson, Mark V. H. (2015-01-02). "Four new Early Devonian ischnacanthid acanthodians from the Mackenzie Mountains, Northwest Territories, Canada: an early experiment in dental diversity". Journal of Vertebrate Paleontology. 35 (1): e948546. doi:10.1080/02724634.2014.948546. ISSN   0272-4634.
  8. 1 2 3 4 5 6 7 8 9 Adrain, Jonathan M.; Wilson, Mark V. H. (1994-09-07). "Early Devonian cephalaspids (Vertebrata: Osteostraci: Cornuata) from the southern MacKenzie Mountains, N.W.T., Canada". Journal of Vertebrate Paleontology. 14 (3): 301–319. doi:10.1080/02724634.1994.10011561. ISSN   0272-4634. JSTOR   4523572.
  9. 1 2 3 4 5 6 7 8 9 10 11 12 Wilson, Mark V. H.; Caldwell, Michael W. (1998-04-10). "The Furcacaudiformes: a new order of jawless vertebrates with thelodont scales, based on articulated Silurian and Devonian fossils from northern Canada". Journal of Vertebrate Paleontology. 18 (1): 10–29. doi:10.1080/02724634.1998.10011031. ISSN   0272-4634. JSTOR   4523870.
  10. 1 2 3 Hanke, Gavin F. (2008). "Promesacanthus eppleri n. gen., n. sp., a mesacanthid (Acanthodii, Acanthodiformes) from the Lower Devonian of northern Canada" (PDF). Geodiversitas. 30 (2): 287–302.
  11. 1 2 Soehn, Kenneth L.; Hanke, Gavin F.; Märss, Tiiu; Wilson, Mark V.H. (2000). "Preliminary vertebrate biostratigraphy of the Avalanche Lake sections (Wenlock, Silurian), southern Mackenzie Mountains, N.W.T., and review of northwestern Canadian vertebrate localities of Silurian Age". Courier Forschungsinstitut Senckenberg. 223: 129–156.
  12. ↑ Hanke, Gavin F; Wilson, Mark VH; Lindoe, L Allan (2001). "New species of Silurian acanthodians from the Mackenzie Mountains, Canada". Canadian Journal of Earth Sciences. 38 (11): 1517–1529. doi:10.1139/e01-039. ISSN   0008-4077.
  13. ↑ Soehn, Kenneth L.; Wilson, Mark V. H. (1990-12-20). "A complete, articulated heterostracan from Wenlockian (Silurian) beds of the Delorme Group, Mackenzie Mountains, Northwest Territories, Canada". Journal of Vertebrate Paleontology. 10 (4): 405–419. doi:10.1080/02724634.1990.10011825. ISSN   0272-4634. JSTOR   4523341.
  14. 1 2 Wilson, Mark V. H.; Caldwell, Michael W. (1993). "New Silurian and Devonian fork-tailed 'thelodonts' are jawless vertebrates with stomachs and deep bodies". Nature. 361 (6411): 442–444. doi:10.1038/361442a0. ISSN   1476-4687.
  15. ↑ Gagnier, Pierre-Yves; Wilson, Mark V. H. (1995-01-01). "New evidences on jaw bones and jaw articulations in acanthodians". Geobios. Premiers Vertandébrandés et Vertandébrandés Infandérieurs. 28: 137–143. doi:10.1016/S0016-6995(95)80101-4. ISSN   0016-6995.
  16. 1 2 3 4 5 6 Hanke, Gavin Frank (2001). "Comparison of an early Devonian acanthodian and putative chondrichthyan assemblage using both isolated and articulated remains from the Mackenzie Mountains, with a cladistic analysis of early gnathostomes". Unpublished PhD Thesis, University of Alberta, Edmonton. doi:10.7939/r3-cqef-jh86.
  17. 1 2 3 4 Wilson, M.V.H.; Hanke, G.F.; Soehn, K.L. (2000). "Diversity and age of the Devonian vertebrate assemblage at MOTH, Mackenzie Mountains, Northwest Territories, Canada". In Antoshkina, A.; Malysheva, E.; Wilson, M.V.H. (eds.). Pan-Arctic Palaeozoic Tectonics, Evolution of Basins and Faunas. Ichthyolith Issues Special Publication 6. Syktyvkar: IGCP 406. pp. 137–141.
  18. ↑ Burrow, Carole J.; Turner, Susan (2018). "Stem chondrichthyan microfossils from the Lower Old Red Sandstone of the Welsh Borderland". Acta Geologica Polonica. 68 (3): 321–334. doi:10.1515/agp-2018-0010.
  19. 1 2 3 4 5 Gagnier, Pierre-Yves; Wilson, Mark V.H. (1996). "Early Devonian acanthodians from northern Canada" (PDF). Palaeontology. 39 (2): 241–258.
  20. 1 2 Blais, Stephanie A. (2017-01-01). Evans, David C. (ed.). "Precise occlusion and trophic niche differentiation indicate specialized feeding in Early Devonian jawed vertebrates". FACETS. 2: 513–530. doi:10.1139/facets-2016-0030. ISSN   2371-1671.
  21. 1 2 3 4 Hanke, Gavin F.; Davis, Samuel P.; Wilson, Mark V. H. (2001-12-14). "New species of the acanthodian genus Tetanopsyrus from northern Canada, and comments on related taxa" . Journal of Vertebrate Paleontology. 21 (4): 740–753. doi:10.1671/0272-4634(2001)021[0740:NSOTAG]2.0.CO;2. ISSN   0272-4634. JSTOR   20062014. S2CID   86098457.
  22. ↑ Hanke, Gavin F.; Davis, Samuel P. (2008). "Redescription of the acanthodian Gladiobranchus probaton Bernacsek & Dineley, 1977, and comments on diplacanthid relationships" (PDF). Geodiversitas. 30 (2): 303–330.
  23. ↑ Newman, Michael J.; Davidson, Robert G.; Blaauwen, Jan L. Den; Burrow, Carole J. (2012). "The Early Devonian Acanthodian Uraniacanthus curtus (Powrie, 1870) n. comb. from the Midland Valley of Scotland" (PDF). Geodiversitas. 34 (4): 739–759. doi:10.5252/g2012n4a2. ISSN   1280-9659. S2CID   54811929.
  24. 1 2 Hanke, Gavin F.; Wilson, Mark V.H. (2010). "The putative stem-group chondrichthyans Kathemacanthus and Seretolepis from the Lower Devonian MOTH locality, Mackenzie Mountains, Canada". Morphology, Phylogeny and Paleobiogeography of Fossil Fishes. Munich: Verlag Dr. Friedrich Pfeil. pp. 159–182.
  25. 1 2 3 4 Hanke, Gavin F.; Wilson, Mark V.H. (2004). "New teleostome fishes and acanthodian systematics". In Arratia, Gloria; Wilson, Mark V.H.; Cloutier, Richard (eds.). Recent Advances in the Origin and Early Radiation of Vertebrates. München: Verlag Dr. Friedrich Pfeil. pp. 189–216. ISBN   3-89937-052-X.
  26. ↑ Hanke, Gavin F.; Davis, Samuel P. (September 2012). "A re-examination of Lupopsyrus pygmaeus Bernacsek & Dineley, 1977 (Pisces, Acanthodii)" (PDF). Geodiversitas. 34 (3): 469–487. doi:10.5252/g2012n3a1. ISSN   1280-9659. S2CID   85622590.
  27. ↑ Burrow, Carole Jan; Murphy, Michael; Turner, Susan (2023-06-06). "Late Silurian to earliest Devonian vertebrate biostratigraphy of the Birch Creek II section, Roberts Mountains, Nevada, U.S.A." PaleoBios. 40 (4): 1–32. doi:10.5070/P940454153. ISSN   2373-8189.
  28. ↑ Blais, Stephanie A.; MacKenzie, Lindsay A.; Wilson, Mark V. H. (2011). "Tooth-Like Scales in Early Devonian Eugnathostomes and the 'Outside-In' Hypothesis for the Origins of Teeth in Vertebrates". Journal of Vertebrate Paleontology. 31 (6): 1189–1199. doi:10.1080/02724634.2011.607992. ISSN   0272-4634.
  29. 1 2 Hanke, Gavin F. (2002). "Paucicanthus vanelsti gen. et sp. nov., an Early Devonian (Lochkovian) acanthodian that lacks paired fin-spines". Canadian Journal of Earth Sciences. 39 (7): 1071–1083. Bibcode:2002CaJES..39.1071H. doi:10.1139/e02-023.
  30. ↑ Hanke, Gavin F.; Wilson, Mark V. H.; Saurette, Fernand J. (2013). "Partial articulated specimen of the Early Devonian putative chondrichthyan Polymerolepis whitei Karatajūtė-Talimaa, 1968, with an anal fin spine" (PDF). Geodiversitas. 35 (3): 529–543. doi:10.5252/g2013n3a2. ISSN   1280-9659.
  31. 1 2 3 Gagnier, P.; Hanke, G.; Wilson, M. (1999). "Tetanopsyrus lindoei gen. et sp. nov., an Early Devonian acanthodian from the Northwest Territories, Canada". Acta Geologica Polonica. 49 (2): 81–96. ISSN   0001-5709.
  32. ↑ Johanson, Zerina; Smith, Moya M. (2003). "Placoderm fishes, pharyngeal denticles, and the vertebrate dentition". Journal of Morphology. 257 (3): 289–307. doi:10.1002/jmor.10124. ISSN   0362-2525.
  33. 1 2 3 4 5 6 Scott, Bradley R; Wilson, Mark V H (2015-03-04). "The Superciliaspididae, a new family of Early Devonian Osteostraci (jawless vertebrates) from northern Canada, with two new genera and three new species". Journal of Systematic Palaeontology. 13 (3): 167–187. doi:10.1080/14772019.2013.863809. ISSN   1477-2019.
  34. ↑ Voichyshyn, Victor (2006). "New osteostracans from the Lower Devonian terrigenous deposits of Podolia, Ukraine" (PDF). Acta Palaeontologica Polonica. 51 (1): 131–142.
  35. ↑ Keating, Joseph N.; Sansom, Robert S.; Purnell, Mark A. (2012). "A new osteostracan fauna from the Devonian of the Welsh Borderlands and observations on the taxonomy and growth of Osteostraci". Journal of Vertebrate Paleontology. 32 (5): 1002–1017. doi:10.1080/02724634.2012.693555. ISSN   0272-4634.
  36. 1 2 Scott, Bradley R.; Wilson, Mark V.H. (2013). "A new species of osteostracan from the Lochkovian (Early Devonian) of the Mackenzie Mountains, with comments on body size, growth, and geographic distribution in the genus Machairaspis". Canadian Journal of Earth Sciences. 50 (2): 127–134. doi:10.1139/cjes-2012-0100. ISSN   0008-4077.
  37. ↑ Hawthorn, Jessica R.; Wilson, Mark V. H.; Falkenberg, Armin B. (2008-12-12). "Development of the dermoskeleton in Superciliaspis gabrielsei (Agnatha: Osteostraci)". Journal of Vertebrate Paleontology. 28 (4): 951–960. doi:10.1671/0272-4634-28.4.951. ISSN   0272-4634. JSTOR   20491029.
  38. 1 2 3 Scott, Bradley R.; Wilson, Mark V. H. (2012). "A new species of Waengsjoeaspis (Cephalaspidomorpha, Osteostraci) from the Early Devonian of northwestern Canada, with a redescription of W. nahanniensis and implications for growth, variation, morphology, and phylogeny". Journal of Vertebrate Paleontology. 32 (6): 1235–1253. doi:10.1080/02724634.2012.694514. ISSN   0272-4634.
  39. ↑ Wilson, M V; Märss, T (2009). "Thelodont phylogeny revisited, with inclusion of key scale-based taxa" (PDF). Estonian Journal of Earth Sciences. 58 (4): 297. doi:10.3176/earth.2009.4.08. ISSN   1736-4728.
  40. 1 2 Pellerin, Nicole M.; Wilson, Mark V.H. (1995). "New evidence for structure of Irregulareaspididae tails from Lochkovian beds of the Delorme Group, Mackenzie Mountains, Northwest Territories, Canada". Geobios. 28: 45–50. doi:10.1016/S0016-6995(95)80085-9.
  41. 1 2 Greeniaus, Jeffrey W.; Wilson, Mark V. H. (2003-06-17). "Fossil juvenile Cyathaspididae (Heterostraci) reveal rapid cyclomorial development of the dermal skeleton". Journal of Vertebrate Paleontology. 23 (2): 483–487. doi:10.1671/0272-4634(2003)023[0483:FJCHRR]2.0.CO;2. ISSN   0272-4634. JSTOR   4524340.
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