What Taxonomic Level Needs Representation on the Ark?

If the answer is "each species alive today", mission impossible. But if family is more like it ...

Mammals:

According to Mammal Species of the World, 5,416 species were identified in 2006. These were grouped into 1,229 genera, 153 families and 29 orders.

Reptiles

Jul 8, 2018 - Number of families: As of Feb 2018 there are 86 families of reptiles (see our taxonomic overview and the phylogenetic tree of squamates for lists). Note that this number is a bit arbitrary, depending on what is called a family (sometimes a subfamily). Number of genera: As of Feb 2018 there are 1199 genera of reptiles.
http://www.reptile-database.org/db-info/SpeciesStat.html

Birds

170 families
https://www.bto.org/about-birds/birdfacts/bird-families

Preliminary total

153 mammals
86 reptiles
170 birds
409

Dinosaurs

Add 15 dinosaur families 424, pterosaurs not included, so 425

"To date, scientists have identified thousands of individual dinosaur species, which can be roughly assigned to 15 major families—ranging from ankylosaurs (armored dinosaurs) to ceratopsians (horned, frilled dinosaurs) to ornithomimids ("bird mimic" dinosaurs)."
https://www.thoughtco.com/main-dinosaur-types-1091963

Amphibians

Shall we be really generous and involve amphibians?
https://amphibiaweb.org/lists/index.shtml

Anura (frogs and toads) families: 55
Caudata families: 10
Gymnophiona families: 10

Where we also ask, whether it's the 75 families or the 3 orders we should be considering as kinds ....

More like total

425, 428 or 500.

If you comprehend that deer and hedgehogs aren't species, but families, you might start seeing sense ....

Yes, for any given place on earth with one typical hedgehog, that hedgehog will typically be a species. In Great Britain, Scandinavia, Italy, France, we deal with Erinaceus europaeus. Meanwhile, in Romania, Austria, Poland, Balkans, Russia, Ukraine, Siberia, Crete, you will instead be dealing with Erinaceus roumanicus. In Anatolia, Mesopotamia, Syria and Holy Land, you will be dealing with Erinaceus concolor. In parts of China, in Korea, in neighbouring parts of Siberia (Amur oblast), you will find Erinaceus amurensis. Four different species of the genus Erinaceus.

Around the Caspian Sea, a long way East of this, into West China, into parts of Afghanistan and Pakistan, into parts of Iran, into SE Turkey, West Syria, Holy Land, Egypt and Libya, you will find Hemiechinus auritus. In Pakistan and India you will also find Hemiechinus collaris. So much for genus Hemiechinus.

It also belongs to the Erinaceinae subfamily of the family Erinaceidae. Erinaceinae are 17 live species in 5 genera. Galericinae is the other subfamily, involving 8 species of moonrat in 5 more genera. Now you may start to comprehend why 153 is the number of mammals' families and why families is a better taxonomic level than species.

Hans Georg Lundahl
Nanterre UL
Franciscan Holy Martyrs of Morocco*
16.I.2019

* Marrochii, in Africa, passio sanctorum quinque Protomartyrum Ordinis Minorum, scilicet Berardi, Petri atque Othonis Sacerdotum, Accursii et Adjuti Laicorum; qui, ob Christianae fidei praedicationem ac Mahumeticae reprobationem legis, post varia tormenta et ludibria, a Saracenorum Rege, scissis gladio capitibus, enecati sunt.