Portland Formation
Geological formation in Connecticut and Massachusetts
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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 4 kilometres (2.5 mi) 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]
| Portland Formation | |
|---|---|
| Stratigraphic range: Hettangian-Sinemurian ~ | |
| Type | Geological formation |
| Unit of | Agawam Group, Newark Supergroup |
| Sub-units | Turners Falls Sandstone & Mount Toby Formation |
| Overlies | East Berlin Formation |
| Lithology | |
| Primary | Sandstone |
| Other | Mudstone, siltstone, limestone |
| Location | |
| Coordinates | 42.3°N 72.5°W |
| Approximate paleocoordinates | 24.0°N 18.6°W |
| Region | Connecticut, Massachusetts |
| Country | United States |
| Extent | Deerfield & Hartford Basins |
  Portland Formation (the United States)  Portland Formation (Massachusetts) | |
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, made by trackmakers including 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]
Color key
|
Notes
Uncertain or tentative taxa are in small text
crossed out taxa are discredited.
| Dinosaurs | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Anomoepus [7] | A. sp. |
|
Hundreds of ornithischian footprints and trackways. | Tracks made by small Ornithischians. |  | |
| Eubrontes[8] | E. sp. |
|
Many theropod footprints and trackways. | Tracks made by medium to large sized theropods likely similar to Dilophosaurus. | _-_close-up.JPG) | |
| Grallator[8] | G. sp. |
|
Many theropod footprints and trackways. | Tracks made by small to medium sized theropods likely similar to Coelophysis. |  | |
| Otozoum [9] | O. sp |
|
Many sauropodomorph trackways. | Tracks made by medium sized Sauropodomorphs. Likely made by animals such as Anchisaurus. |  | |
| Anchisaurus[2] | A. polyzelus[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.[10] |  | ||
| Podokesaurus[2] | P. holyokensis | Massachusetts | Partial postcranial skeleton.[11] | A coelophysoid theropod. The only specimen was destroyed in a fire. |  | |
| Neotheropoda indet.[12] | indeterminate | Massachusetts | Partial humerus. | Estimated to have been 9 meters long, and possibly a semiaquatic piscivore. | ||
| Theropoda indet.[13] | indeterminate | Connecticut | Two specimens and tracks attributed to "Anchisauripus" | The animal was noted as being similar to Coelophysis as well as being slightly larger than some of the largest specimens attributed to Coelophysis. | ||
| Non-dinosaur archosaurs | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Stegomosuchus[14] | S. longipes | Hine's Quarry, Longmeadow | Partial postcranial skeleton. | Originally Stegomus. A small armored "protosuchian" crocodyliform. | _(18125938496).jpg) | |
| Pterosauria indet,[15] | indeterminate | South Hadley, Massachusetts | Partial wrist bone and tooth. | Non-pterodactyloid pterosaur estimated to have a wingspan of 40 cm. | ||
| Fish | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Acentrophorus[16] | A. chicopensis | Material initially referred to the genus Acentrophorus. Most researchers consider the species distinct from Acentrophorus. | ||||
| Redfieldius[17] | R. gracilis | The last surviving redfieldiiform fish. |  | |||
| Semionotus[17] | S. sp. | A semionotid fish. |  | |||
Invertebrate paleofauna
| Insects | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Holcoptera | H. schlotheimi[18] | A coptoclavid beetle known with distinct color pattern. |  | |||
| H. giebeli[19][18] |  | |||||
| Orthoptera[19] | indeterminate | |||||
| Blattaria[19] | indeterminate | |||||
| Polyphaga[19] | indeterminate | An indeterminate polyphagan larvae. Similar to Mormolucoides but larger. | ||||