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While the majority of the soft-bodied animals typically don't have any kind of skeleton, some do, mainly in the form of stiff cuticles (roundworms, water bears) or hydrostatic skeletons (annelids). [5] While lack of a skeleton typically restricts the body size of soft-bodied animals on land, marine representatives can grow to very large sizes.
The majority of animal species are invertebrates; one estimate puts the figure at 97%. [1] Many invertebrate taxa have a greater number and diversity of species than the entire subphylum of Vertebrata. [2] Invertebrates vary widely in size, from 10 μm (0.0004 in) [3] myxozoans to the 9–10 m (30–33 ft) colossal squid. [4]
Baculum of a dog's penis; the arrow shows the urethral sulcus, which is the groove in which the urethra lies. Fossil baculum of a bear from the Miocene. The baculum (pl.: bacula), also known as the penis bone, penile bone, os penis, os genitale, [1] or os priapi, [2] is a bone in the penis of many placental mammals.
Quetzalcoatlus (/ k ɛ t s əl k oʊ ˈ æ t l ə s /) is a genus of azhdarchid pterosaur that lived during the Maastrichtian age of the Late Cretaceous in North America. The type specimen, recovered in 1971 from the Javelina Formation of Texas, United States, consists of several wing fragments and was described as Quetzalcoatlus northropi in 1975 by Douglas Lawson.
The stomach contents, found between the ribcage and hip bones, included the leg and foot bones of two Citipes yearlings. Citipes was a small, birdlike dinosaur that walked on two legs and had a ...
Chordate fossils have been found from as early as the Cambrian explosion over 539 million years ago. [11] Of the more than 81,000 [ 12 ] living species of chordates, about half are ray-finned fishes ( class Actinopterygii ) and the vast majority of the rest are tetrapods , a terrestrial clade of lobe-finned fishes ( Sarcopterygii ) who evolved ...
The world's smallest known vertebrate, Paedophryne amauensis, sitting on a U.S. dime.The dime is 17.9 mm in diameter, for scale. The word amphibian is derived from the Ancient Greek term ἀμφίβιος (amphíbios), which means 'both kinds of life', ἀμφί meaning 'of both kinds' and βίος meaning 'life'.
Researchers have unearthed stone tools that date back to at least 3.3 million years ago, but before this discovery, the oldest known bone tools were found at European sites believed to be 250,000 ...