Ladd Formation
Encyclopedia
The Ladd Formation is a Mesozoic
geologic formation located in Orange County, California
.
remains (mainly hadrosaurid
fragments) are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus
. In 1927 Bernard Nettleton Moore found a hadrosaur maxilla
with teeth while searching for ammonite
s in the formation. In 1950 Marlon V. Kirk found a plesiosaur
centrum (spool of the vertebra). In 1978 Robert Drachuk, also while searching for ammonites, collected a hadrosaur cranial
fragment from a limestone
concretion
. In 1992 Robert D. Hansen found the distal tibia
of a hadrosaur.
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
geologic formation located in Orange County, California
Orange County, California
Orange County is a county in the U.S. state of California. Its county seat is Santa Ana. As of the 2010 census, its population was 3,010,232, up from 2,846,293 at the 2000 census, making it the third most populous county in California, behind Los Angeles County and San Diego County...
.
Paleofauna
DinosaurDinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
remains (mainly hadrosaurid
Hadrosaurid
Hadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper...
fragments) are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
. In 1927 Bernard Nettleton Moore found a hadrosaur maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
with teeth while searching for ammonite
Ammonite
Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct subclass within the Molluscan class Cephalopoda which are more closely related to living coleoids Ammonite, as a zoological or paleontological term, refers to any member of the Ammonoidea an extinct...
s in the formation. In 1950 Marlon V. Kirk found a plesiosaur
Plesiosaur
Plesiosauroidea is an extinct clade of carnivorous plesiosaur marine reptiles. Plesiosauroids, are known from the Jurassic and Cretaceous Periods...
centrum (spool of the vertebra). In 1978 Robert Drachuk, also while searching for ammonites, collected a hadrosaur cranial
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
fragment from a limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
concretion
Concretion
A concretion is a volume of sedimentary rock in which a mineral cement fills the porosity . Concretions are often ovoid or spherical in shape, although irregular shapes also occur. The word 'concretion' is derived from the Latin con meaning 'together' and crescere meaning 'to grow'...
. In 1992 Robert D. Hansen found the distal tibia
Lower extremity of tibia
The lower extremity of the tibia, much smaller than the upper extremity of tibia, presents five surfaces; it is prolonged downward on its medial side as a strong process, the medial malleolus.- Surfaces :...
of a hadrosaur.
| Vertebrates of the Moreno Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Member | Abundance | Notes | Images |
Basilemys |
||||||