| Portland Formation | |
| Type: | Geological formation |
| Age: | Hettangian-Sinemurian ~ |
| Period: | Sinemurian |
| Prilithology: | Sandstone |
| Otherlithology: | Mudstone, siltstone, limestone |
| Region: | Connecticut, Massachusetts |
| Country: |  United States |
| Coordinates: | 42.3°N -72.5°W |
| Paleocoordinates: | 24°N -18.6°W |
| Unitof: | Agawam Group, Newark Supergroup |
| Subunits: | Turners Falls Sandstone & Mount Toby Formation |
| Extent: | Deerfield & Hartford Basins |
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 4km (02miles) 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]
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, which represent ornithischians, theropods, and sauropodomorphs, which are preserved at sites such as Dinosaur Footprints Reservation.[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 | A. polyzelus |
| ||||
| Podokesaurus | P. holyokensis | Massachusetts | Partial postcranial skeleton.[7] | All known remains of this species have been destroyed. | ||
| Neotheropoda sp.[8] | Massachusetts | Partial humerus. | Estimated to have been 9 meters long, and possibly a semiaquatic piscivore. | |||
| Non-Dinosaur Archosaurs | |||||||
|---|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images | |
| Stegomosuchus[9] | S. longipes | Hine's Quarry, Longmeadow | Partial postcranial skeleton. | Originally Stegomus. A small armored "protosuchian" crocodyliform. | |||
| Pterosauria sp.[10] | 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 | |
| Redfieldius[11] | R. gracilis | The last surviving redfieldiiform fish. | |||||
| Semionotus | S. sp. | A semionotid fish. | |||||
| Insects | |||||||
|---|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images | |
| Holcoptera | H. schlotheimi[12] | A coptoclavid beetle. | |||||
| H. giebeli[13] | |||||||
| Orthoptera sp. | An indeterminate orthopteran | ||||||
| Blattaria sp. | An indeterminate cockroach | ||||||