Family Camarasauridae

Originally (especially in old books on dinosaurs) the Brachiosaurs and Camarosaurs were grouped together, with the Diplodocids and Titanosaurs as a seperate branch. Both Brachiosaurs and Camarosaurs have long forelimbs, shortish tails, short high skulls, and more and broader teeth. More recently research has shown that the Titanosaurs are actually related to the Brachiosaurs, the Camarasaurs, Brachiosaurs, and Titanosaurs being collectively referred to as the clade Macronaria. In this respect the Camarasaurs are the most primitive of the Macronarians. However, they also are specialised in specific ways. The skull is short, blunt and relatively large. The teeth are large and spatulate or spoon-like. The neck very strong but inflexible, and apparently strongly upwardly-directed (an adaptation on browsing on trees, unlike the low-feeding diplodocids and euhelopids). A distinguishing mark is the "bifid" (split or two-branched) neural spines (i.e. the upward part of each vertebra is divided into two), the resulting U-shaped trough perhaps for the location of strong tendons. The forelimbs were not as elongated as in the Brachiosaurids, with the fore and hind legs are approximately the same length, the hind legs being only slightly longer. The tail is fairly short, relative to diplodocids. These animals appear to have lived in large herds.

Until fairely recently it was stated that Camarosaurus evolved from the Chinese Euhelopus, but it is more likely that the Chinese forms, with their extraordinarily elongated necks, represented a line of advanced Shunosaurs. Despite their unspecialised structure, Camarasaurs are not known before the early Kimmeridgian epoch, and it is possible that they evolved either from basal Oxfordian Brachiosaurids, or from early Jobaria-like forms

Guild/Ecological niche: gigantic terrestrial high browsing herbivores
Modern equivalent: elephant??? giraffe???
Time: Kimmeridgian to Barremian
Distribution: known with certainty only from Western and middle Laurasia
Evolved from: ? Cetiosauridae or ? Basal Brachiosauridae
Replaced: Cetiosauridae
Replaced by: Titanosaurs
Extinction because of: Cenomonian mass-extinction event? Or Earlier?
Descendents: none
Linnean status: Family
Cladistic status: Monophyletic clade
Parent clade: Macronaria
Adult length: 14 to 18 meters
Adult weight: 10 to 25 tonnes
Preferred habitat/environment: seasonally dry floodplains
Activity period: mostly diurnal, but probably fed and was active almost 24 hours
Metabolism: endothermic when young? gigantotherms (homeotherms) when subadult and adult
Senses: Eyes large, facing sideways; very good all-round (≅270° ?) vision. Hearing and sense of smell moderate.
Intelligence: brain to weight ratio small, at low end of modern reptiles, consciousness guided largely by instinct
Preferred food: mainly conifers - foliage from middle branches, could not reach as high as brachiosaurs
Feeding behaviour: stood motionless or walked very slowly, sweeping neck and head in wide arcs to access all foliage within reach, leaves and twigs cut and crushed with teeth
Food Processing: food ground in gizzard; symbiotic microrganisms in gut process plant amterial
Social behavior: travelled in large herds
Possible Life Cycle: quasi r-strategist, nest excavated with hind feet, eggs covered with dirt or vegetation, then abandoned, young small, active, high metabolism (although perhaps not as high as brachiosaurs). Infant mortality high, but young fast-growing, as they grew larger their metabolism and growth-rate slowed, slowed, became typical gigantotherms, joined the herd as "teenagers"
Movement: erect stance, slow plodding gait. Unlikely to rear on hindlegs. Tererstrial only (poor swimmer).
Walking speed: probably about 3 or 4 kph
Running Speed: no more than 12 kph
Predators: none as healthy adult; young, sick, etc vulnerable to any large theropod
Defense against predators: height and good eyesight allowed early detection of predators; size and safety in herd a good defense, the neck was very strong and could be swung with great force, a single blow would kill a large theropod; stomping with forelegs or kicking with hind-legs could catch any unwary preditor that got to close; for young very rapid growth and possible camoflague markings only protection.

The following cladogram is a simplified version of the ones at Mikko's phylogeny site and Justin Tweet's Thescelosaurus! pages. I have also made the completely arbitrary assumption that the three species of Morrison Camarasaurs which suceed each other chronologically are also an evolutionary succession (a chronospecies so to speak). As usual among dinosaur taxa, there is a lot of generic oversplitting, and the three genera placed in this family are so similiar that they should perhaps be considered subgenera or even species of one genus.

List of Species

Camarosaurus (Lourinhasaurus) alenquerensis (de Lapparent & Zbyszewski, 1957)

comments: Previously mistaken for Apatosaurus, this giant sauropod was one of the first of the Camarosaurids. This species, a robust, average camarasaurid, has recently been placed in a new genus, Lourinhasaurus

comments: Aragosaurus is very similiar to Camarasaurus, and, in view of its later occurance, may be a descendent. It is a very large animal, and shows that Camarasaurs, although suffering local extinctions, happened to survive the terminal Jurassic event quite well.

Comments: This animal was extremely common and dominated the megafauna of the region