Glossary H
Homepage > Glossary H
HINDLIMBS
The hindlimbs are the back legs of an animal. The hindlimbs of most dinosaur
were larger than the forelimbs. Diplodocid dinosaurs (like Diplodocus)
are an exception.
HIRONOSAURUS
(pronounced hi-RON-oh-SAWR-us) Hironosaurus was large, duck-billed dinosaur
from the late Cretaceous Period, about 97.5-65 million years ago. Very
little is known about this hadrosaur since only fragmentary fossils have
been found. This plant-eater was found in Japan. Hironosaurus is an unofficial
name due to a sparsity of fossils.
HISTOLOGY
Histology is the study of tissue structure. A histologist is a scientist
who studies histology.
HISTRIASAURUS
(pronounced HIS-tree-ah-SAWR-us) Histriasaurus (meaning: "Istrian
lizard," for the Istrian peninsula of northwest Croatia, on the Adriatic
Coast) was a large plant-eating dinosaur that lived during the early Cretaceous
Period (from the late Hauterivian to early Barremian, about 126-125 million
years ago). Histriasaurus was a diplodocimorpha, a long-necked, whip-tailed
giant that walked on four columnar legs. It had peg-like teeth and high
vertebral spines. It may have had a sail on its back. Fossils of this
sauropod were found in Croatia. The type species is H. boscarollii, named
for Dario Boscarolli, who discovered the fossil site. Histriasaurus was
named by Dalla Vecchia in 1998. It is probably closely related to, but
more primitive than Rebbachisaurus.
HITCHCOCK, EDWARD B.
Edward B. Hitchcock (1793-1864) was a US clergyman and geologist who found
the first large dinosaur trackways (in Connecticut, USA). He collected
over 20,000 fossil footprints. Hitchcock collected over 20,000 dinosaur
fossil footprints; he thought that the trackways had been made by huge,
extinct birds (and was essentially correct).
HOLMES, ARTHUR
Arthur Holmes (1890 - 1965) was a British geologist who first proposed
the idea of a geologic time scale in 1913. This was soon after the discovery
of radioactivity, and using radio-isotope dating, Holmes estimated that
the Earth was about 4 billion years old - this was much greater than previously
believed.
HOLOCENE
The Holocene (meaning: "entirely recent" in Greek) is the most
recent epoch in geologic time, lasting from about 11,000 years ago until
the present day (the time since the last Ice Age).
Holotype
The holotype of a species is the first specimen to be given the name.
Holotypes are reference specimens kept in museums as a guarantee of the
definition of a species.
HOLTZ, THOMAS
Thomas R. Holtz, Jr. (1965- ) is an American vertebrate paleontologist
and author. Holtz is a lecturer at the Department of Geology, University
of Maryland, College Park. He was born in Los Angeles and spent his early
childhood near Houston, Texas. He was an undergraduate at the Johns Hopkins
University, and received his Ph. D. at Yale University. Holtz's main research
is on the evolution, anatomy, and ecology of theropod dinosaurs (especially
tyrannosaurids). Holtz is the coauthor of The World of Dinosaurs (with
Michael Brett-Surman, illus. by James Gurney - Greenwich Workshop Books,
1998), contributor to The Complete Dinosaur [Dinosaur hunters of the Southern
Continents and other sections] (ed. James O. Farlow and Michael Brett-Surman
- Indiana University Press, 1997), coauthor of the Dinosaur Field Guide
(with Michael Brett-Surman - Random House, 2001), author of the Little
Giant Book of Dinosaurs (2001, Sterling Press), author of the Tyrannosaur
sections of the Univ. of Arizona's Tree of Life classification project
on the Web (2000), and has many other publications.
HOMALOCEPHALE
(pronounced HOMM-ah-low-SEF-ah-lee) Homalocephale (meaning: "Level
head") was a pachycephalosaurid, a thick-skulled dinosaur. Its skull
was relatively flat and had bony knobs along the edges. It was an herbivore
(a plant-eater) about 5 feet (1.5 m) long and weighed about 43 kg. It
walked on two legs and lived during the late Cretaceous Period (80-70
million years ago). An almost complete skeleton was found in Mongolia
in 1901 and named by paleontologists Maryánska and Osmólska
in 1974.
HOMEOSAURUS
Homeosaurus is a genus of sphenodontian, a type of lizard (a reptile similar
to the Tuatara, but not a dinosaur). The earliest-known Homeosaurus dates
from the Triassic period, about 230 million years ago. This quadruped
has long legs and a very long tail. There is still one living species
of Homeosaurus inhabiting New Zealand and some nearby islands.
HOMEOTHERMIC
Homeothermic animals maintain a constant body temperature. Birds and mammals
are homeothermic.
HOMINOIDEA
The Superfamily Hominoidea includes the apes and humans. It includes the
Family Hominidae (people and our close ancestors and relatives), Family
Pongidae (orangutans, chimpanzees, and gorillas), and Family Hylobatidae
(gibbons and siamangs).
HOMINID
Hominids (family Hominidae) are the group that includes people and our
close ancestors and relatives.
HOMOLOGY
Homology is the similarity of characters found in different species that
are due to common descent. Examples include the flippers of whales and
our arms.
HOMOPLASY
Homoplasy is the similarity of characters found in different species that
are NOT from common descent. Examples include the wings of insects and
the wings of pterosaurs. These characters derive from convergent evolution,
parallel evolution, or character reversal.
HOPLITOSAURUS
(pronounced huh-PLEE-toh-SAWR-us) Hoplitosaurus (meaning: "Hoplite
lizard;" a hoplite was an armed soldier) was an ankylosaur, an armored
dinosaur. It had rows of flattened horny plates running along its back.
Hoplitosaurus was an herbivore (a plant-eater) that walked on four legs
and lived during the early Cretaceous Period (135-119 million years ago).
An incomplete fossil was found in South Dakota, USA in 1901 and named
in 1902 by F. A. Lucas.
HOPLOPHONEUS
(pronounced hop-loh-PHONE-ee-us) Hoplophoneus was a relatively small saber-toothed
cat (about 1 1/2 to 2 times the size of a housecat) that lived during
the Oligocene period (from about 40 million to 20 milion years ago). Fossils
have been found in Wyoming, USA. This cat's skull was 6 inches (15 cm)
long. This predator had long, saber-like upper canine teeth that fit into
a socket in its lower jaw. Hoplophoneus was plantigrade (flat-footed,
unlike modern-day cats, which are digitigrade). Its large jaws could open
about 90 degrees, allowing it to stab its victims with its incisors. Classification:
Superfamily Feloidea (cats, mongooses), Family Felidae, Subfamily Machairodontinae,
Genus Hoplophoneus
HOPLOSUCHUS
(pronounced hop-loh-SOOK-us) Hoplosuchus (meaning: "armored crocodile")
was a small, primitive crocodilian from the Jurassic Period. This marsh
dweller was an evolutionary dead-end. This carnivorous reptile was found
in 1909 by paleontologist Earl Douglass, in what is now Dinosaur National
Monument, Utah, USA.
HORN
Horn is an organic substance made mostly of the fibrous protein called
keratin (our nails, hair, bull's horns, feather quills, and horse hoofs
are also made of keratin). Some dinosaurs, like Triceratops, had bone-like
"horns" that may have been covered by a layer of keratin (horn)
when they were alive. Since keratin does not fossilize well, we do not
know if horn covered the bone and if so, how much it was.
HORN CORAL
Horn coral is a type of large, horn-shaped coral (order Rugosa) that lived
as a solitary individual or as a colony. This invertebrate evolved during
the Ordovician Period, roughly 500 million years ago. Horn corals are
important index fossils. Their fossils are also sometimes used to determine
the length of the day (and the year) in the distant past due to the manner
in which they grew.
HORNER, JOHN R.
John R. (Jack) Horner is a US paleontologist (born on June 15, 1946 in
Shelby, Montana) who named: Maiasaura (with Makela, 1979), and Orodromeus
(with D.B. Weishampel, 1988). He discovered the first egg clutches (from
Maiasaura) in the Americas and the first evidence of parental care from
dinosaurs. Horner is the Curator of Paleontology at the Museum of the
Rockies in Bozeman, Montana, USA. Horner attended the University of Montana,
majoring in geology and zoology. Horner is the author of: "Digging
Dinosaurs" (Workman Pub., 1988), "Complete T-rex" (with
D, Lessem, Simon and Schuster,1993), "Maia, A Dinosaur Grows Up"
(Museum of the Rockies, Montana State University, 1985), "Digging
Up Tyrannosaurus rex" (with D, Lessem, 1992), "Dinosaur Eggs
and Babies" (Cambridge University Press, 1994), and "Dinosaur
Lives" (HarperCollins, 1997). Horner was a technical advisor for
the movies Jurassic Park and The Lost World.
Horseshoe Crab
A horseshoe crabs are not actually crabs they are primitive arthropods.
They have a broad plate-like body and a thin spine-like tail. Their ancestry
can be traced back to the Cambrian period, but in wasn't until the Jurassic
period that the true horse-shoe shape developed. By the Late Cretaceous
period, they were less common although five species of horseshoe crab
still exist today.
Horsetail
A group of plants that originated in the Devonian period and were particularly
successful in the Carboniferous period when some species grew up to 30
metres tall. Horsetails are regular symmetrical plants with jointed stems
and circles of leaves. Some species still exist today but none grows taller
than a couple of metres.