Dire wolf (Canis dirus) from Rancho La Brea, Calif.; detail of a mural. From Wikimedia Commons. Public domain.
TAXONOMY & NOMENCLATURE * *How Do We Know This? Like living animals, fossil remains of once-living animals
classified and grouped according to their relationships
each other and to their ancestors.
(ITIS 2010) (Anyonge & Roman 2006) (Lindblad-Toh et al 2005)
(McKenna & Bell 1997) (Tedford et al 2009) (Wilson & Reeder 2005) (Wang et al 2004)
Leidy 1858 for Canis dirus. Linnaeus 1758 for genus Canis
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Carnivora Suborder: Caniformia (dog-like carnivores; includes many extinct families) Family: Canidae (dogs, coyotes, foxes, jackals, wolves; many extinct genera) Genus: Canis (6 living species) Species:Canis dirus EXTINCT Subspecies:Canis dirus guildayi
EXTINCT Subspecies:Canis dirus dirus EXTINCT Suborder: Feliformia
(cat-like carnivores; many extinct families)
Taxonomic History and Nomenclature
Scientific Name: Canis from the Latin for "dog"; dirus from the Latin for "fearful" or "awful"
Two extinct dire wolf subspecies probably exist based on clear size differences and earlier appearance of eastern subspecies. (Anyonge & Roman 2006)
Canis dirus guildayi (smaller individuals, western U.S.)
Phylogeny (Wang et al 2004) (Tedford et al 2009) (Lindblad-Toh et al 2005)
The modern Canid family originated in North America diverging into many species beginning about 10 million years ago (Miocene)
(Lindblad-Toh et al 2005)
Various canids in multiple migrations traveled to Asia, Europe and Africa
A jackal-sized canid, Eucyon (Miocene), is known originally from North America
and later from Africa, Asia and Europe.
Large wolf-like canids evolved from African canid ancestors.
African jackals are most primitive members of the modern wolf-like canids
Wolves, dholes, and African wild dogs came from African and Eurasian ancestor
The genus Canis appears in North America between 11 and 4 million years ago (late Miocene to early Pliocene). (Tedford et al 2009)
Between 3 million and 300,000 years ago (late Pliocene to Pleistocene), the genus Canis extended its range considerably
Large wolf-like species of Canis evolved first in Eurasia.
Wolves belonged to a circum-arctic fauna that invaded North America several times
Canis armbrusteri fossils date to 1.8 million years ago (Early Pleistocene) in southwestern U.S., later in eastern U.S.
Canis armbrusteri gave rise to dire wolves.
Dire wolves (Canis dirus) appeared first in midcontinental U.S.
Dire wolves existed in North and northern South America between 300,000 and 12 ,000 years ago
An eastern subspecies appeared first and was larger.
A western subspecies was smaller and evolved slightly more recently.
Modern gray wolves (Canis lupus) appeared south of the ice sheets by about 100,000 years ago in mid latitude U.S. and co-existed with dire wolves.
By 12,000 years ago dire wolves were extinct.
Gray wolves live throughout the northern hemisphere today.
But eliminated from most of continental U.S., Europe, S.E. China and Indochina. (Wilson & Reeder 2005)
PREHISTORIC DISTRIBUTION & HABITAT * *How Do We Know This? Scientists make sense of fossil
distribution patterns using knowledge of the earth's rocks, global plate
plus genetic and phylogenetic studies.
Ancient habitats are revealed by studies of modern environments where sediments
are deposited, taking into account the chemical processes of fossilization.
(Anyonge & Baker 2006) (Coltrain et al 2004) (Dundas 1999) (Hodnett et al 2009) (Hunt 1996)
(Prevosti & Rincon 2007)
(Stock & Harris 1992)
300,000 to 12,000 years ago (Late Pleistocene)
North America into northern South America (southern Alberta, Canada to southern Bolivia)
Rare in South America
Only 10 fossil sites with dire wolves known to date but lack of exploration may be a factor
More than 136 fossils sites known.
Nearly 4,000 dire wolves found in La Brea asphalt deposits in California
Most common of the Pleistocene canids at La Brea (Stock & Harris 1992)
Extremely variable; forested mountains to open grasslands and plains
Sea level to 2255 m (7400 ft)
In Sonora, Mexico, in environments thought to be a tropical marsh with nearby thorn-scrub, deciduous forest, and grassland.
Pleistocene climate in southern California during time when one of the La Brea asphalt pits collected dire wolves, compared with today:
(Coltrain et al 2004).
PHYSICAL CHARACTERISTICS* *How Do We Know This? Careful study of fossil bone or tooth anatomy yields
much exact information
about placement and strength of muscles, tendons,
ligaments, nerves, and blood vessels.
In rare cases, scales, skin, nails or hairs leave impressions
in sediments. Even more rarely,
actual skin, nails, or hair is preserved.
Body weight is more difficult
to gauge because fat
leaves no impression on the skeleton.
(Turner & Anton 1997) (Anyonge et al 2003) (Anyonge & Baker 2006) (Anyonge & Roman 2006)
Estimated Body Weight: 34-67kg (75-148 lb) (Anyonge & Roman 2006) Head/Body Length: 125 cm (4.1 ft) (Anton & Turner 1997) Height at Shoulder: 80 cm (2.6 ft) Tail Length: 63 cm (2 ft)
A wolf quite similar to the modern wolf except for being heavier, with a broader and more robust skull. (Anyonge & Baker 2006)
(Anyonge et al 2003)
Skulls show evidence of considerable enhancement for attachment of powerful jaw muscles
Cheek bones (zygomatic arches) greatly expanded
Crest down midline of skull (sagittal) is large
Occipital bone in rear of skull has prominent backwards projection
Some earlier studies (Merriam (1912) describe skull features that have little significance in the mechanics of the skull
On average, similar in size to largest of living gray wolves; largest dire wolves would have been larger than living gray wolves. (Binder et al 2002) (Anyonge & Roman 2006)
Weights calculated to be 25% heavier than living gray wolves
Estimates of weight should not be based on femur length,
as in many previously published estimates.
(Anyonge & Roman 2006)
Stress calculations based on cross-sectional measurements of the femur should be more accurate.
Canine teeth have greater bending strength than seen in living dogs of similar size. (Van Valkenburgh & Ruff 1987)
Slicing teeth (P4, the carnassial) on upper jaw larger than those of modern gray wolves (Anyonge & Baker 2006)
Slicing carnassial (M1) on lower jaw is similar to that of typical canids
(Anyonge & Baker 2006)
Not as far back as in bone-crushing hyaena
Wear patterns on teeth show some blunting, suggesting some bone chewing
Teeth not as worn down as seen in bone crushing hyaenas
As in other carnivores studied, the pulp cavity inside teeth closes with age as dentine is deposited (Binder et al 2002)
Can be used to predict age up to 6 or 7 years.
Unknown, assumed similar to modern gray wolf.
Not much difference between male or female body and tooth sizes.
Other Physical Characteristics
In a study of extinct dire wolf skulls compared with an extinct bone-eating dog, modern large gray wolves from Canada and Alaska, and spotted hyaenas:
(Anyonge & Baker 2006)
Out of 15 significant measurements, only 4 differed from modern gray wolves
Skull is flatter (as is modern gray wolf's) than a spotted hyaena's; probably weren't cracking bones like hyaenas do.
Muscle used for chewing and biting (temporalis) could generate more force than seen in modern gray wolves; perhaps had stronger killing bites
Skull not domed like that of bone crushing dogs.
Longevity: assumed similar to modern wolf - 6-8 years.
BEHAVIOR & ECOLOGY* *How Do We Know This? Since direct observation of a fossil animal's behavior
isn't possible, paleontologists use
comparison and contrast with living animals for
guidance. Tracks can sometimes
reveal further clues. Associated animals and
plants found at a fossil site can suggest predator/prey dynamics and dietary options.
(Binder et al 2002) (Hodnett et al 2009) (Van Valkenburgh et al 1990) (Van Valkenburgh & Hertel 1993)
(Van Valkenburgh & Sacco 2002)
Social Life (Van Valkenburgh & Sacco 2002)
Large numbers of dire wolves preserved at La Brea suggest they lived in large groups.
Probably the deposits didn't represent solitary individuals feeding successively
More than 3,000 individuals represented in several tar pits.
Probably monogamous, living in packs like modern gray wolves
Male and females' teeth and skeletons are similar (little dimorphism)
In modern animals, amount of sexual dimorphism correlates with the animal's breeding system
When males' canine teeth much larger, males compete strongly for females and breeding system may be polygamous
When both sexes have similar canine teeth, typically have low level of male-male competition and pair-bonded breeding system as in African wild dogs, dholes, gray wolves.
Many other species of dog-like carnivores found in fossil sites with dire wolves.
(Hodnett et al 2009)
Coyotes, timber wolves, Asiatic wild dogs at San Jacinto Cave (Nuevo Leon, Mexico)
Coyotes, domestic dogs, gray foxes, and timber wolves at La Brea asphalt deposits
Lack of tooth wear scratches on Smilodon suggests they many have left large portions of their kills
(Van Valkenburgh et al 1990)
A co-evolutionary relationship with dire wolves (who could finish eating the kills) proposed by researchers.
Between 15,000 and 12,000 years ago dire wolves may have undergone changes in feeding habits (Van Valkenburgh & Hertel 1003) (Binder et al 2002)
Earlier fossils show more tooth breakage, perhaps signifying more bone-chewing of kills
Later fossils (at 12,000) years ago show less bone consumption and less breakage.
Less bone consumption most likely reflects less competition with other predators for kills as numbers of all these large animals declined.
DIET & FEEDING* *How Do We Know This? Clues to fossil mammals' diets come from not only teeth,
but also skull shape, from fossil dung and gut contents, from microscopic viewing of
wear on teeth, from lab analysis of oxygen, carbon, and nitrogen isotopes
in bone and teeth, and by looking
at diets of similar modern animals.
(Anyonge & Roman 2006) (Coltrain et al 2004) (Ewer 1973) (Fox-Dobbs et al 2003)
(Fox-Dobbs et al 2007) (Harris et al 2004) (Hodnett et al 2009) (Therrien 2005)
(Van Valkenburgh & Ruff 1987) (Van Valkenburgh 1998)
(Van Valkenburgh & Sacco 2002)
Calculated bite force:
129% of modern gray wolves
64% of the extinct American lion
Often took large prey, as inferred from:
Large body size
Carnivorous, meat-eating dentition
Some researchers suggest that, like many canids, probably hunted in packs, normally subdued prey with many shallow, debilitating bites (Ewer 1973) (Therrien 2005)
Other researchers note that teeth and jaws may also have held struggling prey (Van Valkenburgh & Ruff 1987)
Dire wolves had great degree of roundness and greater bending strength in canine teeth, when compared with modern wolves (prey must have not been subdued immediately).
Smilodon, by contrast had more delicate teeth that probably didn't come in contact with the prey's bones (used powerful front limbs to subdue prey)
Studies of twisting and stress forces generated at different points of carnivore jaws reveal:
Like other canids, dire wolves' lower jaws fortified behind the slicing carnassial molars (for bone-crushing),
Dire wolves could crush bones, but not as well as modern wolves
When dire wolves compared to large cats, bite force not as strong in the front of the jaw (where cats use the canine for a killing bite)
Were not specialized predators, fed on whatever megafauna were most abundant. (Fox-Dobbs et al 2007)
Horses were important prey; sloth, mastodon, bison and camel were less common prey.
Fed on medium to large hoofed animals. (Hodnett et al 2009)
Ate both ruminants and non-ruminants (Coltrain et al 2004)
Maximum prey size would have been 300-599 kg (Anyonge & Roman 2006) (Van Valkenburgh & Hertel 1998)
A pack of dire wolves could even have preyed on adult bison. (Anyonge & Roman 2006)
May have also supplemented diet with smaller prey species (Fox-Dobbs et al 2003)
Extinct dire wolves, saber-tooth cats, and American lions all competed for similar prey. (Coltrain et al 2004)
According to nitrogen isotope values of bone
Large numbers of broken teeth suggest high levels of competition for carcasses. (Van Valkenburgh 1998)
May also have scavenged large portions of prey that Smilodon didn't finish.
DISEASES AND PATHOLOGY*
*How do We Know This? Abnormalities in fossils bones may show evidence
of arthritis, cancer, nutritional stress, fractures and more.
(Duckler & Van Valkenburgh 1998)
(Binder et al 2002)
In a study of the general health of several Pleistocene animals (as revealed by x-rays of their bones), dire wolves' health appeared no different than that of modern healthy populations of carnivores.
Bone x-rays can show lines where normal growth is halted and later resumed (called Harris lines)
Frequency of Harris lines very low, similar to health wolves on Isle Royale,
Dental enamel of fossil dire wolves from La Brea tar seeps show almost no defects; a healthy population is indicated even shortly before their extinction.
Tooth breakage commonly seen in fossils from La Brea
(Binder et al 2007)
Broken teeth a feature of living carnivores that often crack large bones.
Tooth breakage data in fossils must be combined with accurate estimates of an animal's age (so that estimates of breakage are independent of an animal's age)
Dire wolf fossils from La Brea at 15,000 years ago show more tooth breakage than ones from 12,000 years ago.
(Binder et al 2002)
Perhaps this reflects more complete consumption of carcasses at 15,000 years ago and more competition with other predators than at 12,000 years ago when predator densities may have been lower.
Important Web Resources (and where to view fossils in museums):
Natural History Museum of Los Angeles County's George C. Page Museum has a web site introducing many of the region's Late Pleistocene animals, including Dire Wolves. The Page Museum at Rancho la Brea displays most of the iconic large mammal fossils and a large number of rarely seen bird fossils from Late Pleistocene times. Visitors can view technicians working in a large fossil preparation lab.
San Diego Natural History MuseumHas a skeletal mount of a Dire Wolf and murals with Dire Wolves by artist William Stout. The museum's displays include many Late Pleistocene fossils plus original oil murals of the flora and fauna in southern California about 20,000 years ago. Museum's web site's Fossil Field Guide has descriptions of many extinct animals from southern California, including dire wolves.
The Paleobiology Database: This site is a scientific organization run by paleontological researchers from around the world. It features taxonomic and distribution information for the entire fossil record.