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Description
As night falls 19 million years ago during the early Miocene on the southern tip of North America, in what is now the Cucaracha Formation of Panama, nocturnal mammals take to the skies at the coastal edge of a forest. A Petauristodon, a type of flying squirrel, glides from tree to tree in search of fruit and nuts, but it is incapable of powered flight like the many Americanycteris cyrtodon around it. A type of leaf-nosed bat, the Americanycteris are part of the only clade of mammals that can truly fly, and they do so as they catch insects over the forest. Some of the bats however are going further from the confines of the forest, their wings carrying them over the several Dadagavialis gunai on the beach and across a stretch of sea to a small island. More islands exist past this one, forming an island chain, and by "island hopping" in the way the bats will eventually reach a new continent, the one that the crocodilians below came from: South America.

I had originally wanted this done for International Bat Appreciation Day but that was April 17th so clearly my procrastination has once again made me late as hell for a thing (there's also several recently named fossil taxa I want to draw but procrastination has prevented me). Named last year in November 2023, Americanycteris is an extinct bat of the family Phyllostomidae, commonly called the New World leaf-nosed bats since they are found in the Americas and have enlarged leaf-like noses. It is known only from fossilized jaw fragments and teeth, which suggests it was an insectivore and comparable in size to the big-eared woolly bat (Chrotopterus auritus), one of the largest living bats in the neotropics reaching a wingspan of 50 centimeters. Although the known material is kinda crap (not uncommon for bats since their light bones don't preserve easily), Americanycteris is significant because it originates from the early Miocene-aged Cucaracha Formation of Panama, meaning it lived at the very southern tip of the North American. Any paleontology enthusiasts here (I assume that's all of you) would know that the Isthmus of Panama (the bit of land connecting North and South America) only formed later during the late Pliocene, and that its formation led to an event called the Great American Biotic Interchange in which species from both continents spread into each other. The phyllostomid bats are a primarily South American group, and fossils of them in South America date as far back as the Miocene, but the existence of Americanycteris in Panama before the formation of the Isthmus suggests that phyllostomids had managed to spread between the American continents long before any land connected them. In fact phyllostomids are not the only animals known to have done this, as other animals like boas, caimans, procyonids, a ground sloth, a terror bird and several more are all known to have crossed from one of the Americas to the other at certain points before the Isthmus formed, which may suggest an island chain existed during the Miocene that allowed these animals to "island hop", swimming/flying from one island to another step by step between the continents. And interestingly, although phyllostomids are today most common in South America, the existence of Americanycteris and an early Oligocene fossil Noctilionoid bat from Florida suggests the group may have first evolved in North America before flying down south.

Aside from one of the oldest phyllostomid bats, the Cucaracha Formation also has other fossil fauna. Dadagavialis is a gavialid (the crocodilian family whose only extant members are the gharial and Tomistoma) known from only skull material, and has been placed in the extinct subfamily Gryposuchinae. Interestingly, most gryposuchines lived in South America and many were marine, suggesting the ancestors of Dadagavialis made the opposite trip to Americanycteris, originating in South America and spreading north across the stretch of sea towards the southern tip of North America. Some fossil teeth of rodents are known from the formation, including those assigned to Petauristodon, a type of squirrel that has been put in the group including the extant flying squirrels (which actually are incapable of true flight and only glide). Because known remains of Petauristodon are all either teeth or kinda suck, it is unclear what exactly the animal looked like or whether it could glide like its modern relatives, but I decided to depict it doing so anyways. According to this abstract , it would appear that two species of Petauristodon were present in the Cucaracha Formation, one of which is the largest known species of the genus. However since the whole study has not yet been published, I do not know the actual size of either species other than the vague adjective "large", so I intentionally left it unclear how far away the squirrel I drew is from the viewer. This way I can bullshit its size and unless the squirrel is kilometers long I should be fine.

Description
As night falls 19 million years ago during the early Miocene on the southern tip of North America, in what is now the Cucaracha Formation of Panama, nocturnal mammals take to the skies at the coastal edge of a forest. A Petauristodon, a type of flying squirrel, glides from tree to tree in search of fruit and nuts, but it is incapable of powered flight like the many Americanycteris cyrtodon around it. A type of leaf-nosed bat, the Americanycteris are part of the only clade of mammals that can truly fly, and they do so as they catch insects over the forest. Some of the bats however are going further from the confines of the forest, their wings carrying them over the several Dadagavialis gunai on the beach and across a stretch of sea to a small island. More islands exist past this one, forming an island chain, and by "island hopping" in the way the bats will eventually reach a new continent, the one that the crocodilians below came from: South America.

I had originally wanted this done for International Bat Appreciation Day but that was April 17th so clearly my procrastination has once again made me late as hell for a thing (there's also several recently named fossil taxa I want to draw but procrastination has prevented me). Named last year in November 2023, Americanycteris is an extinct bat of the family Phyllostomidae, commonly called the New World leaf-nosed bats since they are found in the Americas and have enlarged leaf-like noses. It is known only from fossilized jaw fragments and teeth, which suggests it was an insectivore and comparable in size to the big-eared woolly bat (Chrotopterus auritus), one of the largest living bats in the neotropics reaching a wingspan of 50 centimeters. Although the known material is kinda crap (not uncommon for bats since their light bones don't preserve easily), Americanycteris is significant because it originates from the early Miocene-aged Cucaracha Formation of Panama, meaning it lived at the very southern tip of the North American. Any paleontology enthusiasts here (I assume that's all of you) would know that the Isthmus of Panama (the bit of land connecting North and South America) only formed later during the late Pliocene, and that its formation led to an event called the Great American Biotic Interchange in which species from both continents spread into each other. The phyllostomid bats are a primarily South American group, and fossils of them in South America date as far back as the Miocene, but the existence of Americanycteris in Panama before the formation of the Isthmus suggests that phyllostomids had managed to spread between the American continents long before any land connected them. In fact phyllostomids are not the only animals known to have done this, as other animals like boas, caimans, procyonids, a ground sloth, a terror bird and several more are all known to have crossed from one of the Americas to the other at certain points before the Isthmus formed, which may suggest an island chain existed during the Miocene that allowed these animals to "island hop", swimming/flying from one island to another step by step between the continents. And interestingly, although phyllostomids are today most common in South America, the existence of Americanycteris and an early Oligocene fossil Noctilionoid bat from Florida suggests the group may have first evolved in North America before flying down south.

Aside from one of the oldest phyllostomid bats, the Cucaracha Formation also has other fossil fauna. Dadagavialis is a gavialid (the crocodilian family whose only extant members are the gharial and Tomistoma) known from only skull material, and has been placed in the extinct subfamily Gryposuchinae. Interestingly, most gryposuchines lived in South America and many were marine, suggesting the ancestors of Dadagavialis made the opposite trip to Americanycteris, originating in South America and spreading north across the stretch of sea towards the southern tip of North America. Some fossil teeth of rodents are known from the formation, including those assigned to Petauristodon, a type of squirrel that has been put in the group including the extant flying squirrels (which actually are incapable of true flight and only glide). Because known remains of Petauristodon are all either teeth or kinda suck, it is unclear what exactly the animal looked like or whether it could glide like its modern relatives, but I decided to depict it doing so anyways. According to this abstract , it would appear that two species of Petauristodon were present in the Cucaracha Formation, one of which is the largest known species of the genus. However since the whole study has not yet been published, I do not know the actual size of either species other than the vague adjective "large", so I intentionally left it unclear how far away the squirrel I drew is from the viewer. This way I can bullshit its size and unless the squirrel is kilometers long I should be fine.