Portland Formation
Geological formation in Connecticut and Massachusetts
The Portland Formation is a geological formation in Connecticut and Massachusetts in the northeastern United States. It dates back to the Early Jurassic period. 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).
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.
01Vertebrate paleofauna
Dinosaur coprolites are known from the formation. 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. Other tracks are also known representing animals such as pseudosuchians, turtles, and temnospondyls.
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 | A. sp. |
|
Hundreds of ornithischian footprints and trackways. | Tracks made by small Ornithischians. | ||
| Eubrontes | E. sp. |
|
Many theropod footprints and trackways. | Tracks made by medium to large sized theropods likely similar to Dilophosaurus. | ||
| Grallator | G. sp. |
|
Many theropod footprints and trackways. | Tracks made by small to medium sized theropods likely similar to Coelophysis. | ||
| Otozoum | O. sp |
|
Many sauropodomorph trackways. | Tracks made by medium sized Sauropodomorphs. Likely made by animals such as Anchisaurus. | ||
| Anchisaurus | A. polyzelus |
|
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. | ||
| Podokesaurus | P. holyokensis | Massachusetts | Partial postcranial skeleton. | A coelophysoid theropod. The only specimen was destroyed in a fire. | ||
| Neotheropoda indet. | indeterminate | Massachusetts | Partial humerus. | Estimated to have been 9 meters long, and possibly a semiaquatic piscivore. | ||
| Theropoda indet. | 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 | S. longipes | Hine's Quarry, Longmeadow | Partial postcranial skeleton. | Originally Stegomus. A small armored "protosuchian" crocodyliform. | ||
| Pterosauria indet, | 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 | A. chicopensis | Material initially referred to the genus Acentrophorus. Most researchers consider the species distinct from Acentrophorus. | ||||
| Redfieldius | R. gracilis | The last surviving redfieldiiform fish. | ||||
| Semionotus | S. sp. | A semionotid fish. | ||||
02Invertebrate paleofauna
| Insects | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Holcoptera | H. schlotheimi | A coptoclavid beetle known with distinct color pattern. | ||||
| H. giebeli | ||||||
| Orthoptera | indeterminate | |||||
| Blattaria | indeterminate | |||||
| Polyphaga | indeterminate | An indeterminate polyphagan larvae. Similar to Mormolucoides but larger. | ||||
Sources and credits
This article is adapted from the Wikipedia article “Portland Formation”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
Images, from Wikimedia Commons:
- Anomoepus cropped.png by See original uncropped file, CC BY-SA 4.0
- Dinosaur State Park (Rocky Hill, CT) - close-up.JPG by Daderot, CC BY-SA 3.0
- Grallator footprints.jpg by Smokeybjb, CC BY-SA 3.0
- Otozoum tracks cropped.jpg by Remove "cropped" from file name and see original file, CC BY-SA 4.0
- Anchisaurus NT.jpg by Nobu Tamura (http://spinops.blogspot.com), CC BY-SA 3.0
- Podokesaurus restoration.jpg by FunkMonk, CC BY-SA 3.0
- The American journal of science (1904) (18125938496).jpg by Internet Archive Book Images, No restrictions
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