In Parshat Vaeira (7:9), Moses is commanded to have Aaron throw his staff before Pharaoh and it will turn into a “tannin”.
וְהַשְׁלֵ֥ךְ לִפְנֵֽי־פַרְעֹ֖ה יְהִ֥י לְתַנִּֽין
This plan does not work out as expected and Hashem commands Moses (7:15) to confront Pharaoh again and this time the staff will turn into a serpent.
וְהַמַּטֶּ֛ה אֲשֶׁר־נֶהְפַּ֥ךְ לְנָחָ֖שׁ
(7:15) and the staff that was turned into a serpent
We all know what a serpent is, but what exactly is a “tannin”?
The tannin are mentioned several times in Tanach (a Hebrew acronym for Torah, Prophets and Writings):
In the Book of Genesis (1:21), big tanninim are translated as sea monsters:
וַיִּבְרָא אֱלֹהִים, אֶת-הַתַּנִּינִם הַגְּדֹלִים
And God created the great sea-monsters,
In the Book of Deuteronomy (32:33), tanninim are venomous.
חֲמַת תַּנִּינִם, יֵינָם; וְרֹאשׁ פְּתָנִים, אַכְזָר
Their wine is the venom of tanninim, and the cruel poison of adders.
In Ezekiel (29:3), big tanninim are translated as dragons or crocodiles.
הַתַּנִּים הַגָּדוֹל, הָרֹבֵץ בְּתוֹךְ יְאֹרָיו
the dragons (or great crocodiles) that lie down in the midst of his rivers
In Ezekiel (32:2), tanninim are translated as crocodiles.
וְאַתָּה, כַּתַּנִּים בַּיַּמִּים
You are like crocodiles in the seas.
In Isaiah (27:1) the tannin is referenced to the Leviathan, a coiled serpent that is a gigantic sea creature.
וְעַל לִוְיָתָן, נָחָשׁ עֲקַלָּתוֹן; וְהָרַג אֶת-הַתַּנִּין, אֲשֶׁר בַּיָּם
and on leviathan the winding serpent; and He will slay the tannin that is in the sea.
In Isaiah (51:9) the tannin is referenced to the Rahav, another gigantic sea creature.
הֲלוֹא אַתְּ-הִיא הַמַּחְצֶבֶת רַהַב, מְחוֹלֶלֶת תַּנִּין
Are you not it that hewed Rahab in pieces, that pierced the tannin?
In Jeremiah (51:34) the reference is to the sea.
רִיק בְּלָעַנִי כתיב בְּלָעַנִו כַּתַּנִּין
he has swallowed me like a tannin
In Psalms (74:13, 91:13, 148:7)
שִׁבַּרְתָּ רָאשֵׁי תַנִּינִים, עַל-הַמָּיִם
You did shatter the heads of the tanninim in the waters.
תִּרְמֹס כְּפִיר וְתַנִּין
and a young lion and a serpent you will trample.
הַלְלוּ אֶת-יְהוָה, מִן-הָאָרֶץ-- תַּנִּינִים, וְכָל-תְּהֹמוֹת
Praise the LORD from the land, tanninim, and all deeps
In Job (7:12) a reference to the sea.
הֲיָם אָנִי אִם תַּנִּין
Am I a sea or a tannin,
From these references it appears that the tannin on land are snakes, but when in the water are crocodiles or sea monsters such as the Leviathan or Rahab. Rabbi Eric Levy is of the opinion that they are special creations. In referring back to Genesis 1:13, the big tanninim are the only life forms besides human beings that are “created”. Everything else has been fashioned by God, but not created as such. Rabbi Levy goes out on a limb and theorizes that the big tanninim are dinosaurs. However I have a favorite sea monster that predates the dinosaurs. My favorite is a prehistoric fish called Dunkleosteus terelli. I call him Dunkle for short.
Dunkle is a placoderm, and that makes him an extinct armored fish. He lived about 360-380 million years ago, way before your dinosaurs. Dunkle was 20 feet feet long and weighed more than one ton. His head was armored plated. Dunkle is classified by the scientific community as a hyper-carnivorous apex predator. An apex predator is a predator residing at the top of a food chain upon which no other creatures prey. An apex predator that is hyper-carnivorous gets 70% of its diet from meat. He did not have actual teeth as we know them. Instead of teeth he had sharp “plates” with which he sliced his food. Dunkle was truly king of the sea and a special creation of Hashem. He is my Tannin.