Meridiolestida

Meridiolestida is an extinct clade of mammals known from the Cretaceous and Cenozoic of South America and possibly Antarctica. They represented the dominant group of mammals in South America during the Late Cretaceous. Meridiolestidans were morphologically diverse, containing both small insectivores such as the "sabretooth-squirrel" Cronopio, as well as the clade Mesungulatoidea/Mesungulatomorpha, which ranged in size from the shrew-sized Reigitherium to the dog-sized Peligrotherium. Mesungulatoideans had highly modified dentition with bunodont teeth, and were likely herbivores/omnivores. Meridiolestidans are generally classified within Cladotheria, more closely related to living marsupials and placental mammals (Theria) than to monotremes, barring one study recovering them as the sister taxa to spalacotheriid "symmetrodonts". However, more recent studies have stuck to the cladotherian interpretation. Within Cladotheria, they have often been placed in a group called Dryolestoidea together with Dryolestida, a group of mammals primarily known from the Jurassic and Early Cretaceous of the Northern Hemisphere. However, some analyses have found this group to be paraphyletic, with the meridiolestidans being more or less closely related to therian mammals than dryolestidans are. Meridiolestidans differ from dryolestidans in the absence of a parastylar hook on the molariform teeth and the lack of a Meckelian groove.

Meridiolestida

Hemiauchenia · CC0 · via Wikipedia/Commons. May be a photograph of a specimen, or an artist’s reconstruction — an interpretation of a skeleton, since colour and soft tissue are almost never preserved.

On record

Recorded, not inferred
Sits inside
DryolestoideaPBDB
Diet
insectivorePBDB, for Mammaliaformes
Life habit
scansorialPBDB, for Mammaliaformes
Motility
actively mobilePBDB, for Osteichthyes
Environment
terrestrialPBDB, for Mammalia

Time the record covers

At least 92 million years on record.

The record covers at least 110.1 Mya to 17.5 Mya. No occurrence read is dated outside 113.2 Mya to 16.3 Mya.

Early Cretaceous — about 1 of 28 occurrencesEarly CretaceousLate Cretaceous — about 22 of 28 occurrencesLate CretaceousPaleocene — about 1 of 28 occurrencesPaleoceneEocene — about 0 of 28 occurrencesOligocene — about 0 of 28 occurrencesMiocene — about 4 of 28 occurrencesMiocene115–112 Mya — about 0.5 occurrences112–108 Mya — about 0.5 occurrences88–85 Mya — about 0.1 occurrences85–82 Mya — about 0.4 occurrences82–78 Mya — about 0.4 occurrences78–75 Mya — about 0.4 occurrences75–71 Mya — about 3 occurrences71–68 Mya — about 11 occurrences68–65 Mya — about 7 occurrences65–61 Mya — about 0.7 occurrences24–21 Mya — about 0.8 occurrences21–18 Mya — about 1 occurrence18–14 Mya — about 2 occurrences110.1 Mya17.5 Mya115 Mya14 Mya

28 occurrences of Meridiolestida on record, most of them in the Late Cretaceous. Bar height is expected occurrences, not a count: each fossil is spread across the span it is dated to, so a tall narrow bar means tight dating and a low wide one means loose.

When

28 occurrences

These are dates about fossils, not the animal: the record can only begin after it arose and end before it died out, so either end may reach further. Shares are expected occurrences: a fossil dated to a span is counted partly in each period it straddles. More on what this infers.

Found in

11 formations

Los Alamitos — 41.95°S, 66.33°WLa Colonia — 43.00°S, 67.65°WLa Colonia — 43.11°S, 67.70°WLa Colonia — 43.01°S, 67.63°WChorrillo — 50.50°S, 72.56°WAllen — 39.78°S, 66.70°WSanta Cruz — 51.20°S, 69.12°WSanta Cruz — 51.08°S, 69.13°WDorotea — 50.70°S, 72.53°WSalamanca — 45.50°S, 67.18°WBajo de La Carpa — 38.44°S, 68.73°WSarmiento — 45.67°S, 68.71°WMonte Leon — 50.34°S, 68.96°WCandeleros — 39.63°S, 68.70°W

Loading coastlines…

The named rock units Meridiolestida has been recovered from, largest first. Drawn where the rock is now, not where it formed.

Meridiolestida and its relatives

Late Cretaceous

Where Meridiolestida and its relatives were recorded in the Late Cretaceous.

Found in the same rock

174 taxa

The Paleobiology Database records 17 sites for Meridiolestida, and this reads all of them. The number is how many of those sites it was catalogued from too. The 24 sharing the most are listed.

This is not a list of everything alive at the time. It is only what has come out of the same ground as this animal and been written down.

Entered from

18 references

Each of the 28 occurrences read was entered from one of these publications, ordered by how many each accounts for. This is not a search for papers mentioning the name. 6 further references are not listed. Entries link to doi.org where the Paleobiology Database holds an identifier, and to its own record where it does not. Relayed as the Paleobiology Database holds them, not checked against what they resolve to.

Media and terms

Media content1

Picture of Meridiolestida

Credit
Hemiauchenia
Licence
CC0
Commercial use
the licence allows it

No 3D scan of Meridiolestida was found in MorphoSource and Sketchfab.

Smithsonian Open Access was not reached for this taxon, so this list is what the others held rather than everything there is.

The description on this site

Licence
CC BY-SA 4.0

This is what the site found, which is not the same as what exists.

Keep going

What may have been alongside itDryolestoidea through timeFormations of the Late CretaceousThe world it lived on

Occurrence data from the Paleobiology Database, CC BY 4.0. Rougier et al. 2011