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Extinct animals are not always just modern animals in the past

Foreground: some kind of dog? Background: some other kinds of dog? (Robert Bruce Horsfall paleoart via Wikimedia via Public
Foreground: some kind of dog? Background: some other kinds of dog? (Robert Bruce Horsfall paleoart via Wikimedia via Public Domain)

Biodiversity on Earth is not a static entity; the realization that life has changed over time was a big intellectual and ideological hurdle for (primarily) European proto-scientists to get over and it took them decades to clear the height. But by, say, the late 18th century, most scientists (and increasing numbers of interested amateurs) were able to state that life of the past was not the same thing as life of the modern day.


This sometimes makes science communication difficult. Modern forms of life have formal and informal names associated with them, and there’s been 200+ years of trying to figure out how far back into the past these names go. When do “cats” start? Is “cat” going to be a word that we use exclusively for domestic cats or is it a more inclusive term for “domestic cats and their close relatives”? Do we restrict it to modern cats and their close relatives or do we also include extinct cats? At what evolutionary step do we draw the line between a “cat”, and a “cat relative” or a “cat ancestor”?

It is … to not mince words, impossible in science communication to always use terms accurately. All you can do is try your best to avoid making mistakes and hope that the audience understands what you mean. Yesterday Gizmodo served up four articles about fossil life and I think one of them did a great job on trying to use wording correctly and the other had some difficulties. I’ll discuss the latter and then the former, since the bad example is more illustrative than the good example.


First, a bad example

Motorhead’s Lemmy Will Live On as a Vicious Prehistoric Crocodile


This article uses the word “crocodile” four times. Once by itself in the title, once in the phrase “crocodile relative”, once again by itself in the text, and then another time in the etymology of the name of the genus of the fossil animal. I think it’s probably safe to partially blame a museum press release for the confusion here; the Natural History Museum press release also can’t decide if this animal is a crocodile (used five times) or a crocodile relative (used once).

This confusion reflects informal uncertainty on where to draw the line that demarcates crocodiles from crocodile relatives. We can all agree that an animal like this:

Some kind of riverdog? (Image via Wikimedia user Tomás
Some kind of riverdog? (Image via Wikimedia user Tomás Castelazo)

Is a crocodile. But informally and formally we don’t call this:

A different kind of riverdog? (Image via Wikimedia
via Public Domain)
A different kind of riverdog? (Image via Wikimedia via Public Domain)

A crocodile, we call it an alligator, and although alligators (very roughly) look similar to crocodiles, they’re not crocodiles. There’s an informal term, crocodilian, that is used to lump crocodiles and their close living relatives such as alligators. As we extend back in time to include close extinct relatives, we label (…perhaps not very commonly in informal communication) crocodilians and their close relatives as eusuchians. Eusuchians have some close relatives, and then that group of eusuchians and their close relatives have some close relatives, and if we repeat that process a few times eventually we have combined a lot of fossil and living organisms into a large group we can label as neosuchians.

That group is the one that crocodiles and Lemmysuchus share: Lemmysuchus is one twig on a major branch of Neosuchia, and crocodiles a minor branch with several twigs on the other major branch. Neosuchia is a ~200 million year old group, and crocodiles and Lemmysuchus last had a common ancestor around that time. Humans have close relatives that diverged around the same time as that, here’s a picture of one:

Some third kind of riverdog? (Image via
Wikimedia user Stefan
Some third kind of riverdog? (Image via Wikimedia user Stefan Kraft)

Labeling that as a human, or an ape, or a primate, is as inaccurate as labeling Lemmysuchus as a crocodile. But yesterday a lot of science writers, including a museum press release writer, were inaccurate. A teachable mistake, if anyone is willing to learn from it.

Secondly, a better example

Mammalian Ancestors Went Airborne Earlier Than We Thought

The word “mammal” is one of the trickier words to define scientifically because a lot of what we informally and formally think of as mammal characteristics (grow hair out of the skin, produce milk for offspring from skin glands, usually have high metabolic rates) are things that are not well-preserved in the fossil record. In the modern world there’s three large groups of animals (monotremes, marsupials, and placentals [we’re in that one]) that we collectively term “mammals”, there’s some completely extinct groups that we are very sure are also mammals, and then there’s a hodgepodge of animals that are dang close to being mammals but which don’t seem to be true mammals.


The two newly described “proto-mammals” which this article is about fall somewhere in that hodgepodge; in the past decade different research groups have found haramiyids to be either just barely inside mammals or just outside mammals, and the safest thing to say here would be to label them as “close to, or maybe actually, mammals”. This article does as much, referring to them as “mammalian relative”, “mammalian ancestor”, “mammal-like creature”, and (most accurately) “mammaliaforms”. There’s even some text indicating that controversial question of where haramiyids go:

You might be wondering why I haven’t called these new creatures, which essentially looked like pillow pet-possums, mammals. While they are mammaliaforms, the researchers call them extinct relatives to modern mammals, rather than direct ancestors. Some think they could be mammals, but recent study of the teeth from another member of this group of animals, called the haramiyids, cast doubt on whether they are truly evolutionary ancestors of mammals or a branch off of the evolutionary tree.


Oh my gosh look at all that nuance and a link to an io9 article! Nice.

On the origin of this post

I started writing this as a comment but:
A) it was several hours after publication and authors generally ignore comments not made within a short window after-publication
B) I realized eventually that it’s nonsense to write a two-part comment that extends across two different articles; it’s easier to just write one post about two articles.
C) As with anything critical of work done by the staff, I don’t entirely see the point of using Kinja to attempt to communicate with the staff. Sometimes my critical comments just get literally dismissed, and other times the authors come off as dismissive of their Kinja-based audience:


I know it’s part of the Gawker mindset to be disrespectful to everyone, including the audience, I get that. All of us commenters are filth before the holy altar of the staff, sure, whatever mental construct makes them happy. But inaccurate science communication is not made less inaccurate by having an attitude. Being wrong and being rude is not “better” than just being wrong. And, yes, I know that the staff response to that is ¯\_(ツ)_/¯ so I guess my response to that response is also ¯\_(ツ)_/¯


On the top image

That’s not a cat. Hoplophoneus is a nimravid, it and its nimravid friends are less closely related to cats than hyenas or mongooses are. Crazy how convergent evolution does that. 

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