The Themed Pet Codex shows us pet Theme releases by year, but it doesn't then list the Themes in the order they first appeared. This guide puts Themes in chronological order by the date, and even the time, that the first pet of a Theme came into existence.

Note that this is a work in progress. I will put an Index in this post once there is enough information to justify it.

Also note that I am making these lists of species that I collect. Please feel free to create a chronological list of Themes for any species that you don't see here. I will link to your post in the Index.

Aeridini

Tiger Lily ___________3:46:26 PM ____ 20Apr2014
Royal Viola _________10:47:37 PM ___ 20Apr2014
Spotted Woodpecker _________-_____ 01May2014
Island Flower __________-__________ 25Jul2014
Cranberry Crisp __________-________ 24Oct2014
Harvest Day _____________-________ 27Nov2014
Eventide ___________________-_____ 17Dec2014

Blossoming Rose _______-_____-_____ 06Feb2015
Blue Lotus _______________-________ 24Apr2015
Angelfish ___________-_____________ 21Aug2015
Flaming Soul _____________-________ 08Nov2015
Festival Of Lights __________-________ 23Dec2015

Rain Cloud _________ 12:39:26 PM ___ 20May2016
Camellia Night Rider __ 8:54:42 PM ___ 20May2016
Spring Moon _______ 10:42:47 PM ___ 20May2016
Patriotic __________________________ 02Jul2016
Vampiric ___________.______________ 30Oct2016
Autumn Moon _______._____________ 24Nov2016
Poinsettia _______._________________ 26Dec2016

Azalea Petal 20May2017
Passion Passiflora 25May2017
Natureguard 26May2017
Blazing Fireworks 30Jun2017
Ocean Sunset 31August2017
Nightshade 03Nov2017
Winter Evergreen 26Dec2017

Wildflower 26May2018
Starlight Lily 30May2018
Spring Arcanist 02Jun2018
Wild Blackberry 20Aug2018
Spirit Realm 02Nov2018
Emperor Penguin 23Dec2018

Glowing Garden 21Apr2019
Mourning Cloak 23Apr2019
Rose Arcanist 28Apr2019
Ocean Explorer 12Aug2019
Frosted Apple 28Oct2019
Christmas Pudding 26Dec2019

Dawnbreaker 12:20:48PM 10Apr2020
Frostkeeper 12:20:59PM 10Apr2020
Mistwarden 18Apr2020
Black Swallowtail 23May2020
Spring Peach 26May2020
Rosewood Natureguard 28May2020
Driftwood 19Aug2020
Night Pumpkin 30Oct2020
Winter's Dawn 26Dec2020

Fortuitous Lunar 17Mar2021
Ladybug 12May2021
Fluttering Petals 15May2021
Vintage Arcanist 18May2021
Sea Serpent 09Aug2021
Ancient Artifact 23Oct2021
Autumn Stargazer 28Oct2021
Wintertide Dusk 20Dec2021
Holiday Cheer 25Dec2021

Double Rainbow 14May2022
Petalstorm 17May2022
Wind Serpent 19May2022
Rainbow Pop 13Aug2022
Bountiful Harvest 29Oct2022
Winter Prism 25Dec2022

Prismatic Dewdrop 21May2023
Precocious Daffodil 24May2023
Storm Serpent 25May2023
Crane Flower 14Aug2023
Apple Tree 21Oct2023
Dawning Chill 23Dec2023

Solar Eclipse 08Apr2024
Chocolate Daisy 12May2024
Bright Beginnings 15May2024
Embervine Natureguard 17May2024
Firebird's Feather 12Aug2024
Tranquil Skies 28Oct2024
Halloween 29Oct2024
Zombified 07Nov2024
Inhospitable Beauty 25Dec24

Bulbori (Entries with links are for Pre-tagging Themes. The link shows the first pet of the Theme.)

Valentine ___ 3:27:48 PM ___ 11Feb2013
Chocolate _-_ 3:29:49 PM ___ 11Feb2013
Easter ___________________ 29Mar2013
Patriotic __________________ 04Jul2013
Ashen Fall __________-______ 25Oct2013
Halloween ________________ 31Oct2013
Pumpkin Bread ____________ 05Nov2013
Frosted _______.___________ 17Dec2013
Festive ___________________ 29Dec2013

Lucky 14Mar2014
Chocolate Candy 18Apr2014
White Chocolate 01May2014
Midnight Firefly 25Jul2014
Sweet Tea 03Aug2014
Stuffing 00:09:49 AM 24Oct2014
Devious 2:27:16 PM 24Oct2014
Zombified 30Oct2014
Peppermint Bark 18Dec2014
Tyrielle's Minion 25Dec2014

Breaking Tulip 24Apr2015
Flamboyant Cuttlefish 22Aug2015
Moonlight Chill 30Oct2015
Mint Chocolate Chip 23Dec2015
Midnight Frost 28Dec2015

Golden Heart 12Feb2016
Spring Dawn 20May2016
Hot Tamale Rose 24May2016
Seamist Sun 26Aug2016
Starlight Embers 29Oct2016
Black Widow 03Nov2016
Winter's Night 26Dec2016

Darling Dahlia 20May2017
Black Beauty Gladiolus 24May2017
Blazing Fireworks 30Jun2017
Sand Rabbit 29Aug2017
Coconut Octopus 1:44:03 PM 02Sep2017
Solar Eclipse 4:01:29 PM 02Sep2017
Lost Soul 28Oct2017
Ectoplasma 02Nov2017
Holiday Ornament 22Dec2017
Permafrost 26Dec2017

Forest Shadow 24Feb2018
Lepiota 13May2018
Dancing Butterfly 27May2018
Night Gazer Lily 31May2018
Fresh Perennials 17Aug2018
Siren's Song 19Aug2018
Swamp Tree 30Oct2018
Ripe Pomegranate 03Nov2018
Candle Wax 23Dec2018
Maule's Quince 24Dec2018

Gray Bunny 21Apr2019
Dancing Koi 25Apr2019
Glistening Gem 15Jul2019
Cotton Candy 10Aug2019
Summer Squash 12Aug2019
Fall Harvest 25Oct2019
Toffee Treat 27Oct2019
Underground Depths 30Nov2019
Frosty Soil 23Dec2019
Frozen Berry 27Dec2019

Baby Lamb 23May2020
Lantern Skies 16Aug2020
Pink Hibiscus 28Aug2020
Mysterious Path 28Oct2020
Forbidden Spell 30Oct2020
Darling Deer 23Dec2020
Soft Sunset 25Dec2020

April Rain 15May2021
Sunken Treasure 2:35:41 PM 06Aug2021
Mermaid's Purse 9:04:28 PM 06Aug2021
Morning Mango 08Aug20210
Ancient Mosaic 23Oct2021
Endless Twilight 28Oct2021
Flying Fox 30Oct2021
Tundra Sunrise 18Dec2021
Sugarplum Fairy 21Dec2021

Blooming Spring 14Apr2022
Robin's Egg 14May2022
Wind Chimes 17May2022
Sea Slug 11Aug2022
Coral Reef 13Aug2022
Flint Corn 27Oct2022
Cauldron Crawler 29Oct2022
Pastel Sleet 22Dec2022
Twilight Serenade 25Dec2022

Blossom the Bunny 07Apr2023
Safari 21May2023
Blue Angora 24May2023
Glowing Reef 11Aug2023
Luminescent Depths 15Aug2023
Bubbling Bog 20Oct2023
Rock Candy 22Oct2023
Wonderful Spices 22Dec2023
Playful Snowman 24Dec2023

Daffodil 12May2024
Forest Druid 16May2024
Goliath Beetle 10Aug2024
Tropical Twilight 13Aug2024
Flowering Mums 25Oct2024
Autumn Moon 28Oct2024
Polar Lights 22Dec2024
Twinned Phosphophyllite 25Dec2024

Lunemara:

Harvest Embers 10/25/2013
Halloween 10/31/2013
Autumn Night 11/4/2013
Candlelit 12/17/2013
Festive 12/29/2013

Raspberry Chocolate 2/11/2014
Lucky 3/14/2014
Ladybug 4/18/2014
Early Bloom 5/1/2014
Gladiolus 7/25/2014
Summer Sunrise 8/3/2014
Maple Syrup 10/24/2014
Will 'O Wisp 10/27/2014
Zombified 10/30/2014
Orange Cake 12/17/2014
Tyrielle's Minion 12/25/2014

Sunset Chrysanthemum 4/25/2015
Anthias 8/22/2015
Plumberry Cobbler 10/30/2015
Rosenmunnar Cookie 12/23/2015
Fairy Lights 12/28/2015

Honey Bee 5/20/2016
Canna Annjee 5/24/2016
Patriotic 7/2/2016
Tiger Swallowtail 8/26/2016
Ghostly Lights 10/29/2016
Bottled Moonlight 11/2/2016
Yuletide 12/27/2016

Sunbeam 5/20/2017
Liberty Hosta 5/25/2017
Blazing Fireworks 6/30/2017
Sacred Scarab 8/13/2017
Woodland 8/13/2017
Night Sky 8/13/2017
Thunder Moon 8/29/2017
Moonlit Sea 8/31/2017
Solar Eclipse 9/2/2017
Tree Dryad 9/2/2017
Wilted Willow 10/28/2017
Toxic Cloud 11/2/2017
Chocolate Orange 12/22/2017
Forest Spring 12/26/2017

Wandering Willow 2/24/2018
Moon's Light 5/14/2018
Wildflower 5/26/2018
Slawa Tulip 5/30/2018
Dreamberry 8/17/2018
Flower Wasp 8/20/2018
Sun Kissed Dryad 8/21/2018
Harvest Day 10/30/2018
Carved Pumpkin 11/2/2018
Holiday Candy 12/23/2018
Mint Chocolate 12/23/2018

Forget Me Not 04-21-2019 12:26:58 PM
Blue Banded Bee 4/24/2019
Cracked Geode 07-12-2019 2:34:15 PM
Turquoise Gem 07-14-2019 8:58:45 PM
Moonlight Magnolia 08-10-2019 12:05:42 PM
Rose Scarab 08-12-2019 4:27:20 PM
Mango Chutney 08-12-2019 5:27:08 PM
Autumn Fairy 10-25-2019 12:12:22 PM
Skeletal 10-27-2019 10:14:46 PM
Turtle Dove 12-23-2019 10:29:30 AM
Quiet Dawn 12-25-2019 3:02:17 PM

Cecropia 05-23-2020 2:03:49 PM
Flowery Fairy 05-26-2020 4:37:01 PM
Pasta Salad 08-16-2020 12:03:25 PM
Sunlit Beach 08-18-2020 4:48:31 AM
Golden Pheasant 10-28-2020 12:03:07 PM
Moonlit Sonata 10-30-2020 12:03:13 PM
Elegant Magnolia 12-23-2020 12:03:15 PM
Fig Pudding 12-25-2020 11:31:21 PM

Peacock Butterfly 05-12-2021 12:05:07 PM
Leafy Grub 05-15-2021 10:55:43 AM
Spring Dryad 05-17-2021 8:46:00 AM
Tropical Allure 08-06-2021 2:26:56 PM
Summer Spriteling 08-08-2021 12:26:26 PM
Flickering Umbra 10-23-2021 9:11:29 PM
Deadly Poison 10-28-2021 12:10:34 PM
Demonic Portal 10-30-2021 12:00:47 AM
Snowberry 12-18-2021 12:05:05 PM
Christmas Candle 12-21-2021 5:50:59 AM

Lamb 05-14-2022 3:07:36 PM
Night Blossom 05-18-2022 3:09:31 PM
Moonspring Oracle 05-19-2022 2:04:37 PM
Jade Mantis 08-11-2022 12:00:59 PM
Sunset Moth 08-14-2022 8:29:18 AM
Undersea Scarab 08-15-2022 7:21:59 AM
Calming Woods 10-27-2022 3:03:37 PM
Mischievous Pixie 10-29-2022 3:04:23 PM
Merrymaker 12-22-2022 12:13:45 PM
Frosted Fairy 12-24-2022 4:59:37 PM

Spring Breeze 05-21-2023 12:15:59 PM
Sunrise Flowers 05-25-2023 10:07:45 AM
Fuzzy Bee 08-11-2023 2:21:50 PM
Poison Dart 08-13-2023 4:34:32 PM
Alluring Oracle 08-16-2023 4:35:59 AM
Venomous Elixir 10-20-2023 12:18:05 PM
Fall Garden 10-22-2023 05:55:23 AM
Wooly Bear 12-22-2023 12:04:32 PM
Arctic Stones 12-24-2023 1:03:41 PM

Lily Bouquet 05-12-2024 2:04:24 PM
Wondrous Wasp 05-15-2024 03:42:00 AM
Candy Dryad 05-17-2024 5:03:21 PM
Mossy Tree 08-10-2024 12:04:51 PM
Rosy Maple 08-12-2024 10:55:47 AM
Moon Moth 10-25-2024 12:02:17 PM
Conjured Illusion 10-28-2024 00:28:52 AM
Frozen Pond 12-22-2024 12:19:52 PM
Snowy Trails 12-25-2024 00:27:43 AM

Faelora:

Patriotic 07-04-2013 12:13:57 PM
Sweet Pumpkin 10-25-2013 11:24:05 PM
Halloween 10-31-2013 12:22:05 AM
Poison Flower 11-05-2013 4:30:50 AM
Poinsettia 12-17-2013 12:53:25 AM
Festive 12-29-2013 11:51:19 PM

Rose Champagne 02-11-2014 9:48:43 PM
Lucky 03-14-2014 1:38:53 AM
Spring Passion 04-18-2014 2:56:42 AM
Morning Glory 05-01-2014 11:15:54 AM
Cerulean 07-25-2014 12:06:58 AM
Cave Dweller 08-03-2014 6:47:37 PM
Wilted 10-24-2014 12:41:46 AM
Haunted Woods 10-24-2014 9:17:41 AM
Zombified 10-30-2014 1:05:09 AM
Cherry Cheesecake 12-17-2014 6:17:57 PM
Tyrielle's Minion 12-25-2014 12:30:59 AM

Wildebrim Hosta 04-25-2015 10:21:12 PM
Blue Crab 08-22-2015 11:46:17 AM
Ghostly Chill 10-30-2015 3:37:32 PM
Peppermint Bark 12-24-2015 12:12:53 AM
Snowy Night 12-28-2015 1:43:17 AM

Delicate Bouquet 05-20-2016 12:33:32 PM
Fun Time Gladiolus 05-24-2016 10:41:48 PM
Fire Eel 08-26-2016 12:56:30 PM
Night Terror 10-29-2016 3:18:25 PM
Changing Seasons 11-02-2016 5:37:23 AM
Reindeer 12-26-2016 8:15:00 PM

Forest Fungi 05-20-2017 12:10:03 PM
Floribunda Rose 05-24-2017 10:35:51 PM
Blazing Fireworks 06-30-2017 12:29:58 PM
Grapevine 08-29-2017 1:45:34 PM
Ocean's Blessing 09-02-2017 8:23:24 AM
Solar Eclipse 09-02-2017 4:02:42 PM
Dried Flower 10-28-2017 12:20:32 PM
Ghostly Revenant 11-03-2017 3:05:12 PM
Gilded Wreath 12-22-2017 12:14:08 PM
Evergreen 12-26-2017 8:46:40 AM

Moon's Kiss 02-24-2018 2:32:40 PM
Nature Kissed 05-13-2018 10:33:08 AM
Mystic Spring 05-26-2018 11:34:38 PM
Dutch Tulip 05-30-2018 11:20:22 PM
Midsummer Nights 08-17-2018 3:50:59 PM
Paradise Peach 08-19-2018 11:55:33 AM
Cornucopia 10-30-2018 12:58:10 PM
Ripe Plum 11-02-2018 3:03:53 PM
Holly Tree 12-23-2018 11:48:33 AM
Crocus 12-23-2018 9:54:47 PM

Dawning Equinox 04-21-2019 12:37:59 PM
Flaming Flower 04-25-2019 12:40:32 PM
Emerging Myconid 07-17-2019 5:41:51 PM
Summer Salad 08-10-2019 12:18:22 PM
Enchanted Bloom 08-12-2019 1:12:58 PM
Cave Pool 09-18-2019 12:56:10 AM
Chilling Night 10-25-2019 12:31:09 PM
Rotting Woods 10-27-2019 3:04:13 PM
Blue Spruce 12-23-2019 10:13:31 AM
Dasher 12-25-2019 12:00:02 AM
Aurora Borealis 12-26-2019 3:29:48 PM

Horned Caterpillar 05-23-2020 2:18:54 PM
Lenten Rose 05-27-2020 2:51:25 AM
Wandering Nudibranch 08-16-2020 12:32:09 PM
Strawberry Fields 08-17-2020 4:46:28 PM
Autumn Foliage 10-28-2020 12:08:38 PM
Hidden Woods 10-31-2020 3:01:07 PM
Silver Bells 12-23-2020 12:12:43 PM
Icy Cave 12-25-2020 11:01:51 PM

Sunset Poppy 05-12-2021 12:11:59 PM
Vibrant Bloom 05-15-2021 7:06:09 AM
Coral Bliss 08-06-2021 2:29:18 PM
Berry Dream 08-06-2021 2:37:24 PM
Enchanted Ember 10-22-2021 5:34:02 PM
Rowan Tree 10-28-2021 12:07:27 PM
Somber Forest 10-30-2021 9:18:47 PM
Winter Prairie 12-18-2021 12:07:06 PM
Festive Garland 12-21-2021 8:13:44 AM

Forest Spirit 05-14-2022 3:05:43 PM
Stargazer Lily 05-18-2022 2:05:44 AM
Plum Pie 08-11-2022 12:02:16 PM
Triggerfish 08-15-2022 12:37:30 PM
Bountiful Harvest 10-27-2022 3:04:51 PM
Silver Garden Spider 10-29-2022 7:18:43 PM
Frosted Pine 12-22-2022 12:10:35 PM
Frosty Jubilations 12-24-2022 11:08:10 PM

Elven Woods 05-08-2023 2:37:48 PM
Dawn's Sunlight 05-08-2023 2:37:51 PM
Lemon Zest 05-21-2023 12:16:57 PM
River Mount 05-24-2023 9:50:16 PM
Lavender Breeze 08-11-2023 2:12:38 PM
Tropical Sunset 08-14-2023 10:10:08 AM
Eerie Echoes 10-20-2023 12:01:07 PM
Juicy Pomegranate 10-21-2023 5:25:56 AM
Mimic Poison Frog 10-22-2023 4:00:25 AM
Ceremonial Elven 10-24-2023 9:01:32 AM
Spring Blossom 11-22-2023 2:30:08 AM
Snow Robin 12-22-2023 12:08:32 PM
Merrymaking 12-24-2023 5:13:35 PM

Easter Surprise 03-29-2024 12:02:10 PM
Wildflower Meadow 05-12-2024 2:27:46 PM
Morning Sky 05-15-2024 02:12:25 AM
Tropical Punch 08-10-2024 12:05:24 PM
Perseids 08-12-2024 10:55:44 AM
Sweater Weather 10-25-2024 12:02:46 PM
Dark Fairy 10-27-2024 5:06:00 PM
Icy Allure 12-22-2024 12:22:46 PM
Boysenberry 12-24-2024 12:30:24 PM
Glacial Wayfarer 12-25-2024 4:01:51 PM