← Geological formations

Portland

302 occ. 58 taxa (8 genera) 1 countries
Description

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 and the floodplain of a river. 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 to the late Hettangian and Sinemurian ages.

Genera
8 genera
Eubrontes
Dinosaurs
Valid Ichnogenus 9 occ. · 250 Ma
Platypterna
Dinosaurs
Valid Ichnogenus Formal taxon 3 occ. · 227 Ma
Anomoepus
Dinosaurs
Valid Ichnogenus 3 occ. · 237 Ma
Plectropterna
Dinosaurs
Valid Ichnogenus Formal taxon 2 occ. · 201 Ma
Grallator
Dinosaurs
Valid Ichnogenus 2 occ. · 250 Ma
Plesiornis
Dinosaurs
Valid Ichnogenus Formal taxon 1 occ. · 227 Ma
Anchisaurus
Dinosaurs
Valid 1 occ. · 201 Ma
Anchisauripus
Dinosaurs
Valid Ichnogenus Formal taxon 1 occ. · 247 Ma
Portland
click to enlarge
Original figure caption: .mw-parser-output .smallcaps{font-variant:small-caps}The Middletown Slab covered with the Footprints of Carnivorous Dinosaurs. The tracks are in high relief. Additional notes: Most if not all of these tridactylous (i.e. three-toed) footprints/tracks (but not the actual trackmaker!) are referred to as Grallator or as Grallator-type trace fossils. “High relief” means that these are actually casts of footprints forming a positive relief on the lower surface of the sandstone slab (so-called positive hyporelief). The material that originally formed the mud over which the dinosaurs walked was too friable to be recovered from the quarry in one piece. The slab consists of so called ‘brownstone’ which is the trading name of the sandstone quarried at Middletown, Connecticut. This sandstone belongs to the Lower Jurassic Portland Formation of the Hartford Basin (“Connecticut Valley”) and thus to the upper part of the Newark Supergroup. The trackmakers probably were relatively small ‘primitive’ theropod dinosaurs (coelophysoids) such as Podokesaurus the remains of which were recovered from Lower Jurassic deposits of the Hartford Basin. © Richard S. Lull · Public domain · Wikipedia
Temporal range
Triassic
Jurassic
Cretaceous
Paleogene
Neogene
252 201 145 66 0 Ma
Geological group / Member
Agawam 302
Top countries
🇺🇸 United States 302
Depositional environments
Fluvial-lacustrine indet. 204
Terrestrial indet. 66
Small lake 32
Top collectors
E. Hitchcock 125
D. Marsh 100
Hitchcock 46
J. Deane 33
H. Hammer 27
Marsh 26
Deane 20
J. Bryant 17
P. Moody 14
W. Clark 11
J. Barratt 6
W. Gringras 4
Collection activity by decade
1800s 14
1810s 1
1830s 66
1840s 34
1850s 70
1860s 14
1870s 1
1880s 4
1900s 6
1910s 1
1930s 2
1960s 4