Reptilia · Squamata
Phrynosoma mcalliiHallowell, 1852
Flat-tail Horned Lizard
Photograph placed in the public domain, CC0, via iNaturalist
A ground-dwelling, day-active, meat-eating lizard from the Nearctic region, reaching 109 mm snout to vent.
Once published as Anota mcallii — those names reach this page.
Reptilia › Squamata › Phrynosomatidae › Phrynosoma
- Grows to
- 109.2mm
- greatest recorded
- Eats
- Carnivorous
- Active
- Diurnal
- Lives up to
- 20years
Longer than 79% of all species in Phrynosomatidae anyone has measured.
The bar is the rank itself: its length is the share of the family this animal exceeds. The chart below is the family’s real spread, on a logarithmic scale because body length here runs from 47 to 175 mm. The solid rule is this animal. Every bar is a count of real species, and nothing on this figure is estimated.
What is known
43 sourced facts, each taken from a named scientific dataset. How to read these.
Cited from a dataset unless a row is marked otherwise.
Standing in the world
- Still living
- Extant
- Conservation status
- Near Threatened
- Status assessed · the year the Red List last looked
- 2007
- Population trend
- Decreasing
The animal itself
- Limbs
- Four legs
- Venomous
- No
- Fangs
- None
- Longest recorded life
- 20years
- Body temperature when active · measured in the wild
- 35.5°C96 °F
- Body temp in the wild · mean, when active
- 33.2–37.8°C92–100 °F
6 in nature, 9 in captivity (http://www.azgfd.gov/w_c/edits/documents/Phrymcal.d_004.pdf), 8 (Grimsley et al. 2019), at least 20 years in captivity (Heimes 2022)
mean body temperature of active individuals in nature
body temperature of active animals in nature
Size
- Length snout to vent · greatest recorded
- 109.2mm4.25 in
- Length snout to vent · adult female mean
- 69mm2.75 in
- Largest female · snout to vent
- 69mm2.75 in
- Hatchling length · snout to vent
- 34mm1.25 in
- Largest juvenile · snout to vent
- 34mm1.25 in
- Body mass · greatestcomputed
- 39.95g1.4 oz
- Body mass at hatchingmeasured
- 1.5g0.05 oz
max 109.22 mm SVL (Feldman et al. 2016)
snout-vent length; the source column mixes this with straight carapace length
computed from length by a family-level allometric equation, not weighed
How it lives
- Diet
- Carnivorous
- How it hunts
- Sit and wait
- Active
- Diurnal
- Where it lives
- Terrestrial
- Habitat
- Desert, Shrubland
- Biome
- Deserts & Xeric Shrublands
- Active season · months of the year
- 5–9months
- Region
- Nearctic
- Mainland or island
- Mainland
- Highest it lives · above sea level
- 500m
- Range size
- 31,422km²
- Density
- 0.41–3.44per hectare
insects (mainly ants, Pianka and Parker 1975, Stebbins and McGinnis 2018, Heimes 2022), most ant-specialist diet (Jones and Lovich 2009)
Sit and Wait
e.g., Rorabaugh and Lemos-Espinal 2016, Heimes 2022
0-300 (Rorabaugh and Lemos-Espinal 2016), below sea level to 250 (Stebbins and McGinnis 2018), 0 to about 500 (Heimes 2022)
Breeding
- Reproduction
- Oviparous
- Average clutch
- 4.95eggs
- Eggs or young per clutch
- 2–10eggs
- Mean clutch
- 4.5–5.4eggs
- Clutches in a year
- 1.5per year
- Clutches a year
- 1–2per year
- First breeds at
- 12–24months
2-7, mean 4.5 (Goldberg 2011), 3-10 (Lemm 2006, Stebbins and McGinnis 2018), 3-7 (Rorabaugh and Lemos-Espinal 2016), max 8 (Grimsley et al. 2019), up to 10 (Grismer and Grismer 2022), 3-10, usually 4-7 (Heimes 2022), Dominguez-Guerrero et al. 2022 (mean 4.7),
Naming and history
- Suborder
- Sauria
- Infraorder
- Pleurodonta
- Subspecies
- No
- Described by
- Hallowell
- Moved to another genus · since it was first described
- Yes
- Described in
- 1852
- Type locality
- USA
Keeping one
17 in × 17 in × 10.5 in(44 × 44 × 27 cm)
Minimum length × width × height, for one animal. Bigger is always better.
The standard sizes ground-dwelling species at 4 × 4 × 2.5 times snout-vent length.
Mindestanforderungen an die Haltung von Reptilien (Sachverständigengutachten), German Federal Ministry for Nutrition, Agriculture and Forestry, Animal Welfare Division, 10 January 1997. The standard states these floor areas are recommendations rather than binding limits.
From this animal’s own snout-vent length of 4.25 in (109.2 mm), at 4 × 4 × 2.5 times it, following the German federal welfare standard — how this is worked out.
Active animals measured in the wild averaged 96 °F (35.5 °C).
Mean body temperature of active individuals measured in nature. A measurement of the animal, not a setting for a thermostat.
Feeding
A prey item should be no wider than the space between the animal's eyes.
Widely used across reptile husbandry references. The stated reason is that the gap approximates the width of the throat, so wider prey is associated with impaction. This is established practice, not a measurement.
5kJ per day
Worked out for an animal of 40 g, the heaviest recorded for Flat-tail Horned Lizard — so it is the top of the range, not a figure for a particular animal. Weigh yours and the number will be lower.
An upper estimate, not a feeding target, and not veterinary advice. The equation covers only what an animal burns staying alive, so a growing, gravid or recovering animal needs more — and it was measured on wild animals, which move far more than one in an enclosure. Body condition and a vet who knows the species are what a feeding decision should rest on. Where this comes from.
What nobody knows
These are not gaps in our research. No scientific dataset records them for this species — and saying so is information you cannot get from a reference that simply leaves a field out.
- — Length snout to vent · adult male mean
- — Length snout to vent · adult mean
- — Length nose to tail · greatest recorded
- — Female length · mean, nose to tail
- — Length nose to tail · adult male mean
- — Length nose to tail · adult mean
- — Largest male · snout to vent
- — Largest female · shell length
- — Largest male · shell length
- — Hatchling length · nose to tail
- — Largest juvenile · shell length
- — Egg length
- — Egg width
- — Body mass · a typical adult
- — Body mass · adult female, mean
- — Preferred body temperature · chosen in a laboratory gradient
- — Eats arthropods
- — Eats vertebrates
- — Eats plant matter
- — How the young develop
- — Gestation or incubation
- — Hatchling length · smallest recorded
- — Hatchling length · largest recorded
- — Age at first breeding · female
- — Mature from · youngest recorded
- — Mature by · oldest recorded
- — Size at maturity · smallest recorded
- — Size at maturity · largest recorded
- — Colour on the back
- — Pattern on the back
- — Pupil
- — Sex decided by
- — Red List criteria
- — Home range · largest recorded
- — Active in
- — Lowest it lives · above sea level
Others in Phrynosomatidae
Take this data
Everything on this page is available as data under CC BY 4.0 — use it freely, credit it, no permission needed.
This species as JSON · the whole dataset
Cite this page
The Reptile & Amphibian Encyclopedia (2026). Phrynosoma mcallii. Retrieved 2026-09-08, from https://www.allanglescreatures.com/species/phrynosoma-mcallii
@misc{phrynosoma_mcallii_2026,
title = {Phrynosoma mcallii},
author = {{The Reptile & Amphibian Encyclopedia}},
year = {2026},
url = {https://www.allanglescreatures.com/species/phrynosoma-mcallii}
}Sources
- Meiri, S. (2024). SquamBase — a database of squamate (Reptilia: Squamata) traits. Global Ecology and Biogeography. Public domain (CC0).
- Oskyrko, O. et al. (2024). ReptTraits: a comprehensive dataset of ecological traits in reptiles. Scientific Data. Used under CC BY 4.0.
- Catalogue of Life (dataset 3LR), used under CC BY.