Blastoidea

From Palaeos

o Deuterostomia
`--+--Helicoplacoidea
   `--+--Camptostroma
        `--+--Thecocystidae
           `--+--Edrioasteroidea
              `--+--Cyclocystoidea
                 `--+==Eocrinoidea
                    |  `==Cystoidea
                    |     `--Blastoidea
                    `--+--o Eleutherozoa
                       |  |--o Asterozoa
                       |  |  |--Ophioxenikos
                       |  |  `--+--Asteroidea
                       |  |     `--Ophiuroidea
                       |  `--o Echinozoa
                       |       |--Echinoidea
                       |       `--+--Holothuroidea
                       |          `--Ophiocistioidea
                       `--+--Homalozoa
                          `--+--Echmatocrinus
                             `--Crinoidea

The 80th plate from Ernst Haeckel's Kunstformen der Natur, depicting Blastoidea

[edit] Introduction

The Blastoidea are a group of extinct, Palaeozoic echinoderms characterised by a long stalk with a calyx and theca at the top, making them appear similar in appareance to contemporary stalked echinoderms such as Crinoids, Cystoids, etc.

The fragile and slender arms or brachioles are attach near the mouth of the individual. The grooved ambulacral areas extend away from the mouth along the sides of the theca. They had a complex internal respiratory system which differentiates the blastozoan classes from other echinoderms. The morphology of the blastoids and other blastozoans has led some workers to suggest that the blastozoans lacked tube feet, and thus possibly a water vascular system - another feature which would differentiate them from all other echinoderms. However, this theory is still controversial.

[edit] Information

• Phylum: Echinodermata
  • Subphylum: Blastozoa
    • Class: Blastoidea

Author: Say, 1825

Lifestyle: Suspension feeding high tiered sessile benthos

Environment: Sublittoral zone although doubtless some species would have lived deeper; found clear to silty, moderately agitated ocean bed from shallow continental or inland sea to continental shelf and it could be assumed deeper waters.

Stratigraphic range: Ordivician to Permian (most common during the Mississippian (Early Carboniferous)

[edit] Phylogeny

[edit] Dendrogram

<==Blastoidea [Blastozoa]
   |  i. s.: Codonaster conicus Whidborne 1898 [=Codaster conicus]
   |         Neoschismatidae
   |         Ambolostomatidae
   |         Diploblastidae
   |--Fissiculata
   `--Spiraculata
        |  i. s.: Nucleocrinus [Nucleoblastidae, Nucleocrinidae]
        |         Schizoblastus [Schizoblastidae]
        |         Nymphaeoblastus [Nymphaeoblastidae]
        |         Eleutherocrinus
        |         Granatoblastidae
        |           |--Cryptoblastus
        |           |--Heteroblastus
        |           `--Acentrotremites
        |         Pentephyllum
        |         Zygocrinus
        |--Pentremitida
        |--Granatocrinidae [Granatocrinida]
        |    |--Xinjiangoblastus ornatus
        |    `--Mesoblastus Etheridge & Carpenter 1886
        |         |--M. crenulatus (Roemer 1851) (see below for synonymy)
        |         `--M. glaber
        `--Troosticrinidae [Troosticrinida]
             |--Uyguroblastus conicus
             |--Belocrinus [incl. Belemnocrinus Munier-Chalmas 1876 non White 1862]
             |--Metablastus
             |--Tricoelocrinus
             `--Troostocrinus reinwardti

Mesoblastus crenulatus (Roemer 1851) [=Pentatrematites crenulatus, Pentremites crenulatus]

* Type species of generic name indicated

[edit] References

Jaekel, O. 1918. Phylogenie und System der Pelmatozoen. Paläontologische Zeitschrift 3: 1-128.

Lane, N. G., C. G. Maples & J. A. Waters. 2001. Revision of Late Devonian (Famennian) and some Early Carboniferous (Tournaisian) crinoids and blastoids from the type Devonian area of north Devon. Palaeontology 44 (6): 1043-1080.

Moore, R. C., N. G. Lane, H. L. Strimple, J. Sprinkle & R. O. Fay. 1978. Inadunata. In Treatise on Invertebrate Paleontology pt. T. Echinodermata 2. Crinoidea (R. C. Moore & C. Teichert, eds.) vol. 2 pp. T520-T759. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).

Waters, J. A., C. G. Maples, N. G. Lane, S. Marcus, Liao Z.-T., Liu L., Hou H.-F. & Wang J.-X. 2003. A quadrupling of Famennian pelmatozoan diversity: New Late Devonian blastoids and crinoids from northwest China. Journal of Paleontology 77 (5): 922-948.

[edit] Credits

Phylogeny CKT080212; Introduction and Info MAK061116