Reptilia · Squamata
Petrosaurus thalassinusCope, 1863
Baja California Rock Lizard
Photograph by MarvalPhotography19, CC BY, via iNaturalist
A rock-dwelling, day-active, omnivorous lizard from the Nearctic region, reaching 175 mm snout to vent.
Once published as Uta repens, Uta thalassina — those names reach this page.
Reptilia › Squamata › Phrynosomatidae › Petrosaurus
- Grows to
- 175mm
- greatest recorded
- Eats
- Omnivorous
- Active
- Diurnal
- Lives up to
- 20years
Longer than 99% 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
41 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
- Least Concern
- Status assessed · the year the Red List last looked
- 2007
- Population trend
- Stable
The animal itself
- Limbs
- Four legs
- Venomous
- No
- Fangs
- None
- Longest recorded life
- 20years
- Preferred body temperature · chosen in a laboratory gradientmeasured
- 31.3–35.2°C88–95 °F
- Body temperature when active · measured in the wild
- 35.95°C97 °F
- Body temp in the wild · mean, when active
- 34.8–37.1°C95–99 °F
Slavens and Slavens 1999: 4.9; EOL, Wikipedia: 20 years, Zuniga-Vega et al. 2016: 20, 4264 days (=11.5 years, Foster et al. 2019; captivity, alive)
mean body temperature of active individuals in nature
body temperature of active animals in nature
Size
- Length snout to vent · greatest recorded
- 175mm7 in
- Length snout to vent · adult female mean
- 95.8mm3.75 in
- Largest female · snout to vent
- 94.6mm3.75 in
- Hatchling length · snout to vent
- 32.5mm1.25 in
- Largest juvenile · snout to vent
- 31.5mm1.25 in
- Body mass · greatestcomputed
- 141.1g5 oz
- Body mass at hatchingmeasured
- 1.26g0.04 oz
Heimes 2022 (rarely exceed 150 but max 175 mm)
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
- Omnivorous
- Active
- Diurnal
- Where it lives
- Saxicolous
- Habitat
- Forest, Rocky
- Biome
- Tropical & Subtropical Dry Broadleaf Forests
- Region
- Nearctic
- Mainland or island
- Mainland
- Elevation · above sea level
- 240–2020m
- Range size
- 7546km²
(Grismer 2002, Cardona-Botero et al. 2020), about 50% arthropods and 50% plants, also subadults of own species (Aguirre and Gatica 2010), plants and usually insects (Stebbins and McGinnis 2018), invertebrates, leaves, flowers and seeds, and cannibalistic (Heimes 2022)
Diurnal, diurnal and heliothermic (Heimes 2022)
(e.g., Olberding et al. 2016, Cardona-Botero et al. 2020, Heimes 2022), primarily saxicolous, occasionally forages on the ground (Stebbins and McGinnis 2018)
max 2020 (Heimes 2022)
Breeding
- Reproduction
- Oviparous
- Sex decided by
- Genes, XX/XY
- Average clutch
- 13.8eggs
- Eggs or young per clutch
- 4–21eggs
- Mean clutch
- 8.6–19eggs
- Clutches a year
- 1per year
- First breeds at
- 24months
4-18, mean 8.6 (Goldberg and Beaman 2004, Aguirre and Gatica 2010, Jimenez‐Arcos et al. 2017, mean also cited in Dominguez-Guerrero et al. 2022), Foster et al. 2019 (2 females laid clutchers of 21 and 19 and 19 and 18 eggs in consecutive years), 4-18 but more than 20 in captivity (Heimes 2022)
Naming and history
- Suborder
- Sauria
- Infraorder
- Pleurodonta
- Subspecies
- No
- Described by
- Cope
- Moved to another genus · since it was first described
- Yes
- Described in
- 1863
- Type locality
- Mexico
Keeping one
2 ft 4 in × 2 ft 4 in × 17 in(70 × 70 × 44 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.
Lives on rock, so stable hard surfaces and basking ledges suit it.
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 7 in (175 mm), at 4 × 4 × 2.5 times it, following the German federal welfare standard — how this is worked out.
In a laboratory thermal gradient this species settled at 88–95 °F (31.3–35.2 °C).
Preferred body temperature, recorded in a laboratory gradient where the animal could choose freely. 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.
16kJ per day
Worked out for an animal of 141 g, the heaviest recorded for Baja California Rock 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
- — Eats arthropods
- — Eats vertebrates
- — Eats plant matter
- — How it hunts
- — How the young develop
- — Gestation or incubation
- — Clutches in a year
- — 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
- — Red List criteria
- — Active season · shortest recorded
- — Active season · longest recorded
- — Density · lowest recorded
- — Density · highest recorded
- — Home range · largest recorded
- — Active in
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). Petrosaurus thalassinus. Retrieved 2026-09-08, from https://www.allanglescreatures.com/species/petrosaurus-thalassinus
@misc{petrosaurus_thalassinus_2026,
title = {Petrosaurus thalassinus},
author = {{The Reptile & Amphibian Encyclopedia}},
year = {2026},
url = {https://www.allanglescreatures.com/species/petrosaurus-thalassinus}
}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.