Portland Formation

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The Portland Formation is a geological formation in Connecticut and Massachusetts in the northeastern United States.[1] It dates back to the Early Jurassic period.[2] The formation consists mainly of sandstone laid down by a series of lakes (in the older half of the formation) and the floodplain of a river (in the younger half). The sedimentary rock layers representing the entire Portland Formation are over Script error: No such module "convert". thick and were formed over about 4 million years of time, from the Hettangian age (lower half) to the late Hettangian and Sinemurian ages (upper half).[3]

In 2016, the paleontologist Robert E. Weems and colleagues suggested the Portland Formation should be elevated to a geological group within the Newark Supergroup (as the Portland Group), and thereby replacing the former name "Agawam Group". They also reinstated the Longmeadow Sandstone as a formation (within the uppermost Portland Group); it had earlier been considered identical to the Portland Formation.[4]

Vertebrate paleofauna

Dinosaur coprolites are known from the formation.[2] This formation and the underlying East Berlin Formation are well-known for its numerous well-preserved dinosaur tracks, which represent ornithischians, theropods, and sauropodomorphs, which are preserved at sites such as Dinosaur Footprints Reservation.[2][5] Other tracks are also known representing animals such as pseudosuchians, turtles, and temnospondyls.[6]

Dinosaurs
Genus Species Location Stratigraphic position Material Notes Images
Anchisaurus[2] A. polyzelus[2]
  • Connecticut[2]
  • Massachusetts[2]
 Several specimens. A relatively small basal Sauropodomorph. Many Otozoum tracks in the formation that may belong to Anchisaurus could have been made by potentially even larger specimens of the genus.[7]
File:Anchisaurus NT.jpg
Podokesaurus[2] P. holyokensis Massachusetts Partial postcranial skeleton.[8] A coelophysoid theropod. The only specimen was destroyed in a fire.
File:Podokesaurus restoration.jpg
Neotheropoda sp.[9] Massachusetts Partial humerus. Estimated to have been 9 meters long, and possibly a semiaquatic piscivore.
Theropoda sp.[10] Connecticut Bones and tracks attributed to "Anchisauripus"
Non-dinosaur archosaurs
Genus Species Location Stratigraphic position Material Notes Images
Stegomosuchus[11] S. longipes Hine's Quarry, Longmeadow Partial postcranial skeleton. Originally Stegomus. A small armored "protosuchian" crocodyliform.
File:The American journal of science (1904) (18125938496).jpg
Pterosauria sp.[12] South Hadley, Massachusetts Partial Wrist and tooth. Non-pterodactyloid pterosaur estimated to have a wingspan of 40 cm.
Fish
Genus Species Location Stratigraphic position Material Notes Images
Acentrophorus[13] A. chicopensis Material initially referred to the genus Acentrophorus. Most researchers consider the species distinct from Acentrophorus.
Redfieldius[14] R. gracilis The last surviving redfieldiiform fish. File:Redfieldius gracilis.jpg
Semionotus[14] S. sp. A semionotid fish. File:Semionotus bergeri.jpg

Invertebrate paleofauna

Insects
Genus Species Location Stratigraphic position Material Notes Images
Holcoptera H. schlotheimi[15] A coptoclavid beetle. File:Holcoptera schlotheimi elytron NHMUK I.6653.jpg
H. giebeli[16]
Orthoptera sp.[16] An indeterminate orthopteran.
Blattaria sp.[16] An indeterminate cockroach.

See also

References

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  1. ↑ Portland Formation - USGS
  2. ↑ a b c d e f g h Weishampel et al., 2004, pp.530–532
  3. ↑ Olsen, P.E. (2002). Script error: No such module "citation/CS1".
  4. ↑ Script error: No such module "Citation/CS1".
  5. ↑ Script error: No such module "Citation/CS1".
  6. ↑ Script error: No such module "citation/CS1".
  7. ↑ Script error: No such module "Citation/CS1".
  8. ↑ "Table 3.1," in Weishampel et al., 2004, p.48
  9. ↑ McMenamin, M. (2021). Large neotheropod from the Lower Jurassic of Massachusetts. AcademiaLetters, Article 3591. Script error: No such module "CS1 identifiers". by the author — Open Access — Distributed under CC BY 4.0
  10. ↑ Script error: No such module "citation/CS1".
  11. ↑ Script error: No such module "Citation/CS1".
  12. ↑ Script error: No such module "citation/CS1".
  13. ↑ https://www.researchgate.net/publication/351559379_The_first_Upper_Permian_amphibian_from_the_Dolomites
  14. ↑ a b Script error: No such module "citation/CS1".
  15. ↑ Script error: No such module "citation/CS1".
  16. ↑ a b c Script error: No such module "citation/CS1".

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Bibliography

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