Portland Formation
Stratigraphic range: Hettangian- Sinemurian ~199–195  Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
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°18′N 72°30′W / 42.3°N 72.5°W / 42.3; -72.5
Approximate paleocoordinates	24°00′N 18°36′W / 24.0°N 18.6°W / 24.0; -18.6
Region	Connecticut, Massachusetts
Country	USA
Extent	Deerfield & Hartford Basins
Portland Formation (the United States) Show map of the United States Portland Formation (Massachusetts) Show map of Massachusetts

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]

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]
Podokesaurus [2]	P. holyokensis	Massachusetts		Partial postcranial skeleton. [7]	All known remains of this species have been destroyed.[ citation needed]
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 [11]	S. sp.				A semionotid fish.

Invertebrate paleofauna

Insects
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Holcoptera	H. schlotheimi [12]				A coptoclavid beetle.
	H. giebeli [13]
Orthoptera sp. [13]					An indeterminate orthopteran
Blattaria sp. [13]					An indeterminate cockroach

See also

• List of dinosaur-bearing rock formations

References

Bibliography

• Weishampel, David B.; Dodson, Peter; Osmólska, Halszka, eds. (2004). The Dinosauria, 2nd edition. Berkeley: University of California Press. ISBN  0-520-24209-2. Retrieved 2019-02-21.